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Арсеньев Александр СергеевичДоктор химических наук, Профессор Заведующий отделом (Отдел структурной биологии), Руководитель подразделения (Лаборатория биомолекулярной ЯМР-спектроскопии), Заведующий лабораторией (Центр коллективного пользования "Биоорганика") Тел.: Эл. почта: aars@nmr.ru |
Избранные публикации
- (2018). Phase Transitions in Small Isotropic Bicelles. Langmuir 34 (11), 3426–3437
[+]Isotropic phospholipid bicelles are one of the most prospective membrane mimetics for the structural studies of membrane proteins in solution. Recent works provided an almost full set of data regarding the properties of isotropic bicelles; however, one major aspect of their behavior is still under consideration: the possible mixing between the lipid and detergent in the bilayer area. This problem may be resolved by studying the lipid phase transitions in bicelle particles. In the present work, we investigate two effects: phase transitions of bilayer lipids and temperature-induced growth of isotropic bicelles using the NMR spectroscopy. We propose an approach to study the phase transitions in isotropic bicelles based on the properties ofP NMR spectra of bilayer-forming lipids. We show that phase transitions in small bicelles are "fractional", particles with the liquid-crystalline and gel bilayers coexist in solution at certain temperatures. We study the effects of lipid fatty chain type and demonstrate that the behavior of various lipids in bilayers is reproduced in the isotropic bicelles. We show that the temperature-induced growth of isotropic bicelles is not related directly to the phase transition but is the result of the reversible fusion of bicelle particles. In accordance with our data, rim detergents also have an impact on phase transitions: detergents that resist the temperature-induced growth provide the narrowest and most expressed transitions at higher temperatures. We demonstrate clearly that phase transitions take place even in the smallest bicelles that are applicable for structural studies of membrane proteins by solution NMR spectroscopy. This last finding, together with other data draws a thick line under the long-lasting argument about the relevance of small isotropic bicelles. We show with certainty that the small bicelles can reproduce the most fundamental property of lipid membranes: the ability to undergo phase transition.
ID:2069 - (2017). Impact of membrane partitioning on the spatial structure of an S-type cobra cytotoxin. J. Biomol. Struct. Dyn. , 1–16 [+]
Cobra cytotoxins (CTs) belong to the three-fingered protein family. They are classified into S- and P-types, the latter exhibiting higher membrane-perturbing capacity. In this work, we investigated the interaction of CTs with phospholipid bilayers, using coarse-grained (CG) and full-atom (FA) molecular dynamics (MD). The object of this work is a CT of an S-type, cytotoxin I (CT1) from N.oxiana venom. Its spatial structure in aqueous solution and in the micelles of dodecylphosphocholine (DPC) were determined by (1)H-NMR spectroscopy. Then, via CG- and FA MD-computations, we evaluated partitioning of CT1 molecule into palmitoyloleoylphosphatidylcholine (POPC) membrane, using the toxin spatial models, obtained either in aqueous solution, or detergent micelle. The latter model exhibits minimal structural changes upon partitioning into the membrane, while the former deviates from the starting conformation, loosing the tightly bound water molecule in the loop-2. These data show that the structural changes elicited by CT1 molecule upon incorporation into DPC micelle take place likely in the lipid membrane, although the mode of the interaction of this toxin with DPC micelle (with the tips of the all three loops) is different from its mode in POPC membrane (primarily with the tip of the loop-1 and both the tips of the loop-1 and loop-2).
ID:1943 - (2017). Structural and Dynamic "Portraits" of Recombinant and Native Cytotoxin I from Naja oxiana: How Close Are They? Biochemistry 56 (34), 4468–4477 [+]
Today, recombinant proteins are quite widely used in biomedical and biotechnological applications. At the same time, the question about their full equivalence to the native analogues remains unanswered. To gain additional insight into this problem, intimate atomistic details of a relatively simple protein, small and structurally rigid recombinant cardiotoxin I (CTI) from cobra Naja oxiana venom, were characterized using nuclear magnetic resonance (NMR) spectroscopy and atomistic molecular dynamics (MD) simulations in water. Compared to the natural protein, it contains an additional Met residue at the N-terminus. In this work, the NMR-derived spatial structure of uniformly (13)C- and (15)N-labeled CTI and its dynamic behavior were investigated and subjected to comparative analysis with the corresponding data for the native toxin. The differences were found in dihedral angles of only a single residue, adjacent to the N-terminal methionine. Microsecond-long MD traces of the toxins reveal an increased flexibility in the residues spatially close to the N-Met. As the detected structural and dynamic changes of the two CTI models do not result in substantial differences in their cytotoxicities, we assume that the recombinant protein can be used for many purposes as a reasonable surrogate of the native one. In addition, we discuss general features of the spatial organization of cytotoxins, implied by the results of the current combined NMR and MD study.
ID:1923 - (2017). New Disulfide-Stabilized Fold Provides Sea Anemone Peptide to Exhibit Both Antimicrobial and TRPA1 Potentiating Properties. Toxins (Basel) 9 (5), [+]
A novel bioactive peptide named τ-AnmTx Ueq 12-1 (short name Ueq 12-1) was isolated and characterized from the sea anemone Urticina eques. Ueq 12-1 is unique among the variety of known sea anemone peptides in terms of its primary and spatial structure. It consists of 45 amino acids including 10 cysteine residues with an unusual distribution and represents a new group of sea anemone peptides. The 3D structure of Ueq 12-1, determined by NMR spectroscopy, represents a new disulfide-stabilized fold partly similar to the defensin-like fold. Ueq 12-1 showed the dual activity of both a moderate antibacterial activity against Gram-positive bacteria and a potentiating activity on the transient receptor potential ankyrin 1 (TRPA1). Ueq 12-1 is a unique peptide potentiator of the TRPA1 receptor that produces analgesic and anti-inflammatory effects in vivo. The antinociceptive properties allow us to consider Ueq 12-1 as a potential analgesic drug lead with antibacterial properties.
ID:1914 - (2016). Structure of purotoxin-2 from wolf spider: modular design and membrane-assisted mode of action in arachnid toxins. Biochem. J. 473 (19), 3113–26 [+]
Traditionally, arachnid venoms are known to contain two particularly important groups of peptide toxins. One is disulfide-rich neurotoxins with a predominance of β-structure that specifically target protein receptors in neurons or muscle cells. The other is linear cationic cytotoxins that form amphiphilic α-helices and exhibit rather non-specific membrane-damaging activity. In the present paper, we describe the first 3D structure of a modular arachnid toxin, purotoxin-2 (PT2) from the wolf spider Alopecosa marikovskyi (Lycosidae), studied by NMR spectroscopy. PT2 is composed of an N-terminal inhibitor cystine knot (ICK, or knottin) β-structural domain and a C-terminal linear cationic domain. In aqueous solution, the C-terminal fragment is hyper-flexible, whereas the knottin domain is very rigid. In membrane-mimicking environment, the C-terminal domain assumes a stable amphipathic α-helix. This helix effectively tethers the toxin to membranes and serves as a membrane-access and membrane-anchoring device. Sequence analysis reveals that the knottin + α-helix architecture is quite widespread among arachnid toxins, and PT2 is therefore the founding member of a large family of polypeptides with similar structure motifs. Toxins from this family target different membrane receptors such as P2X in the case of PT2 and calcium channels, but their mechanism of action through membrane access may be strikingly similar.
ID:1568 - (2016). Towards universal approach for bacterial production of three-finger Ly6/uPAR proteins: Case study of cytotoxin I from cobra N. oxiana. Protein Expr. Purif. 130, 13–20
[+]Cytotoxins or cardiotoxins is a group of polycationic toxins from cobra venom belonging to the 'three-finger' protein superfamily (Ly6/uPAR family) which includes small β-structural proteins (60-90 residues) with high disulfide bond content (4-5 disulfides). Due to a high cytotoxic activity for cancer cells, cytotoxins are considered as potential anticancer agents. Development of the high-throughput production methods is required for the prospective applications of cytotoxins. Here, efficient approach for bacterial production of recombinant analogue of cytotoxin I from N. oxiana containing additional N-terminal Met-residue (rCTX1) was developed. rCTX1 was produced in the form of E. coli inclusion bodies. Refolding in optimized conditions provided ∼6 mg of correctly folded protein from 1 L of bacterial culture. Cytotoxicity of rCTX1 for C6 rat glioma cells was found to be similar to the activity of wild type CTX1. The milligram quantities of (13)C,(15)N-labeled rCTX1 were obtained. NMR study confirmed the similarity of the spatial structures of recombinant and wild-type toxins. Additional Met residue does not perturb the overall structure of the three-finger core. The analysis of available data for different Ly6/uPAR proteins of snake and human origin revealed that efficiency of their folding in vitro is correlated with the number of proline residues in the third loop and the surface area of hydrophobic residues buried within the protein interior. The obtained data indicate that hydrophobic core is important for the folding of proteins with high disulfide bond content. Developed expression method opens new possibilities for structure-function studies of CTX1 and other related three-finger proteins.
ID:1599 - (2016). Central loop of non-conventional toxin WTX from Naja kaouthia is important for interaction with nicotinic acetylcholine receptors. Toxicon 119, 274–9 [+]
'Three-finger' toxin WTX from Naja kaouthia interacts with nicotinic and muscarinic acetylcholine receptors (nAChRs and mAChRs). Mutagenesis and competition experiments with (125)I-α-bungarotoxin revealed that Arg31 and Arg32 residues from the WTX loop II are important for binding to Torpedo californica and human α7 nAChRs. Computer modeling suggested that loop II occupies the orthosteric binding site at α7 nAChR. The similar toxin interface was previously described as a major determinant of allosteric interactions with mAChRs.
ID:1598 - (2016). Secreted Isoform of Human Lynx1 (SLURP-2): Spatial Structure and Pharmacology of Interactions with Different Types of Acetylcholine Receptors. Sci Rep 6, 30698 [+]
Human-secreted Ly-6/uPAR-related protein-2 (SLURP-2) regulates the growth and differentiation of epithelial cells. Previously, the auto/paracrine activity of SLURP-2 was considered to be mediated via its interaction with the α3β2 subtype of the nicotinic acetylcholine receptors (nAChRs). Here, we describe the structure and pharmacology of a recombinant analogue of SLURP-2. Nuclear magnetic resonance spectroscopy revealed a 'three-finger' fold of SLURP-2 with a conserved β-structural core and three protruding loops. Affinity purification using cortical extracts revealed that SLURP-2 could interact with the α3, α4, α5, α7, β2, and β4 nAChR subunits, revealing its broader pharmacological profile. SLURP-2 inhibits acetylcholine-evoked currents at α4β2 and α3β2-nAChRs (IC50 ~0.17 and >3 μM, respectively) expressed in Xenopus oocytes. In contrast, at α7-nAChRs, SLURP-2 significantly enhances acetylcholine-evoked currents at concentrations <1 μM but induces inhibition at higher concentrations. SLURP-2 allosterically interacts with human M1 and M3 muscarinic acetylcholine receptors (mAChRs) that are overexpressed in CHO cells. SLURP-2 was found to promote the proliferation of human oral keratinocytes via interactions with α3β2-nAChRs, while it inhibited cell growth via α7-nAChRs. SLURP-2/mAChRs interactions are also probably involved in the control of keratinocyte growth. Computer modeling revealed possible SLURP-2 binding to the 'classical' orthosteric agonist/antagonist binding sites at α7 and α3β2-nAChRs.
ID:1597 - (2016). Characterization of Small Isotropic Bicelles with Various Compositions. Langmuir 32 (26), 6624–37 [+]
Structural studies of membrane proteins are of great importance and interest, with solution and solid state NMR spectroscopy being very promising tools for that task. However, such investigations are hindered by a number of obstacles, and in the first place by the fact that membrane proteins need an adequate environment that models the cell membrane. One of the most widely used and prospective membrane mimetics is isotropic bicelles. While large anisotropic bicelles are well-studied, the field of small bicelles contains a lot of "white spots". The present work reports the radii of particles and concentration of the detergents in the monomeric state in solutions of isotropic bicelles, formed by 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC), 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate (CHAPSO), and sodium cholate, as a function of lipid/detergent ratio and temperature. These parameters were measured using (1)H NMR diffusion spectroscopy for the bicelles composed of lipids with saturated fatty chains of different length and lipids, containing unsaturated fatty acid residue. The influence of a model transmembrane protein (membrane domain of rat TrkA) on the properties of bicelles and the effect of the bicelle size and composition on the properties of the transmembrane protein were investigated with heteronuclear NMR and nuclear Overhauser effect spectroscopy. We show that isotropic bicelles that are applicable for solution NMR spectroscopy behave as predicted by the theoretical models and are likely to be bicelles rather than mixed micelles. Using the obtained data, we propose a simple approach to control the size of bicelles at low concentrations. On the basis of our results, we compared different rim-forming agents and selected CHAPS as a detergent of choice for structural studies in bicelles, if the deuteration of the detergent is not required.
ID:1569 - (2016). Cell-free expression of the APP transmembrane fragments with Alzheimer's disease mutations using algal amino acid mixture for structural NMR studies. Protein Expr. Purif. 123, 105–11 [+]
Structural investigations need ready supply of the isotope labeled proteins with inserted mutations n the quantities sufficient for the heteronuclear NMR. Though cell-free expression system has been widely used in the past years, high startup cost and complex compound composition prevent many researches from the developing this technique, especially for membrane protein production. Here we demonstrate the utility of a robust, cost-optimized cell-free expression technique for production of the physiologically important transmembrane fragment of amyloid precursor protein, APP686-726, containing Alzheimer's disease mutations in the juxtamembrane (E693G, Arctic form) and the transmembrane parts (V717G, London form, or L723P, Australian form). The protein cost was optimized by varying the FM/RM ratio as well as the amino acid concentration. We obtained the wild-type and mutant transmembrane fragments in the pellet mode of continuous exchange cell-free system consuming only commercial algal mixture of the (13)C,(15)N-labeled amino acids. Scaling up analytical tests, we achieved milligram quantity yields of isotope labeled wild-type and mutant APP686-726 for structural studies by high resolution NMR spectroscopy in membrane mimicking environment. The described approach has from 5 to 23-fold cost advantage over the bacterial expression methods described earlier and 1.5 times exceeds our previous result obtained with the longer APP671-726WT fragment.
ID:1570 - (2016). Structural Basis of p75 Transmembrane Domain Dimerization. J. Biol. Chem. 291 (23), 12346–57 [+]
Dimerization of single span transmembrane receptors underlies their mechanism of activation. p75 neurotrophin receptor plays an important role in the nervous system, but the understanding of p75 activation mechanism is still incomplete. The transmembrane (TM) domain of p75 stabilizes the receptor dimers through a disulfide bond, essential for the NGF signaling. Here we solved by NMR the three-dimensional structure of the p75-TM-WT and the functionally inactive p75-TM-C257A dimers. Upon reconstitution in lipid micelles, p75-TM-WT forms the disulfide-linked dimers spontaneously. Under reducing conditions, p75-TM-WT is in a monomer-dimer equilibrium with the Cys(257) residue located on the dimer interface. In contrast, p75-TM-C257A forms dimers through the AXXXG motif on the opposite face of the α-helix. Biochemical and cross-linking experiments indicate that AXXXG motif is not on the dimer interface of p75-TM-WT, suggesting that the conformation of p75-TM-C257A may be not functionally relevant. However, rather than mediating p75 homodimerization, mutagenesis of the AXXXG motif reveals its functional role in the regulated intramembrane proteolysis of p75 catalyzed by the γ-secretase complex. Our structural data provide an insight into the key role of the Cys(257) in stabilization of the weak transmembrane dimer in a conformation required for the NGF signaling.
ID:1571 - (2016). Cell Free Expression and Purification of the Fragments of the Receptor Tyrosine Kynases of the EGFR Family, Containing the Transmembrane Domain with the Juxtamembrane Region, for Structural Studies. BIOLOGICHESKIE MEMBRANY 33 (2), 124–132 [+]
The EGFR/HER receptor family of an epidermal growth factor represents an important class of the receptor tyrosine kinases playing the key role in the control of cell growth and differentiation in mammalian cells, as well as in the development of a number of pathological processes, including oncogenesis. Binding of a ligand to the extracellular domains initiates switching of the EGFR/HER receptor between the alternative dimeric states that causes the allosteric activation of kinase domains in cell cytoplasm. The transmembrane (TM) domain and adjacent flexible regions alternatively interacting with either membrane surface or kinase domains are directly involved in the complex conformational transition in EGFR/HERs. Here we report on a highly efficient system of the cell free production of the EGFR/HER TM domains with functionally important juxtamembrane (JM) regions for the investigation of the molecular basis of biochemical signal transduction across the cell membrane. To increase the efficiency of synthesis of the EGFR/HER TM-JM fragments of the receptors, we used two N-terminal expression tags, which significantly increased the protein yield. In the case of the TM-JM fragments of EGFR (residues 638–692) and HER2 (residues 644–700), the method allowed us to obtain milligram quantities of the 13C,15N-labeled protein for structural and biophysical investigations in the membrane-mimicking environments using high-resolution heteronuclear NMR spectroscopy.
ID:1622 - (2016). HER2 Transmembrane Domain Dimerization Coupled with Self-Association of Membrane-Embedded Cytoplasmic Juxtamembrane Regions. J. Mol. Biol. 428 (1), 52–61 [+]
Receptor tyrosine kinases of the human epidermal growth factor receptor (HER or ErbB) family transduce biochemical signals across plasma membrane, playing a significant role in vital cellular processes and in various cancers. Inactive HER/ErbB receptors exist in equilibrium between the monomeric and unspecified pre-dimerized states. After ligand binding, the receptors are involved in strong lateral dimerization with proper assembly of their extracellular ligand-binding, single-span transmembrane, and cytoplasmic kinase domains. The dimeric conformation of the HER2 transmembrane domain that is believed to support the cytoplasmic kinase domain configuration corresponding to the receptor active state was previously described in lipid bicelles. Here we used high-resolution NMR spectroscopy in another membrane-mimicking micellar environment and identified an alternative HER2 transmembrane domain dimerization coupled with self-association of membrane-embedded cytoplasmic juxtamembrane region. Such a dimerization mode appears to be capable of effectively inhibiting the receptor kinase activity. This finding refines the molecular mechanism regarding the signal propagation steps from the extracellular to cytoplasmic domains of HER/ErbB receptors.
ID:1369 - (2016). A novel lipid transfer protein from the dill Anethum graveolens L.: isolation, structure, heterologous expression, and functional characteristics. J. Pept. Sci. 22 (1), 59–66 [+]
A novel lipid transfer protein, designated as Ag-LTP, was isolated from aerial parts of the dill Anethum graveolens L. Structural, antimicrobial, and lipid binding properties of the protein were studied. Complete amino acid sequence of Ag-LTP was determined. The protein has molecular mass of 9524.4 Da, consists of 93 amino acid residues including eight cysteines forming four disulfide bonds. The recombinant Ag-LTP was overexpressed in Escherichia coli and purified. NMR investigation shows that the Ag-LTP spatial structure contains four α-helices, forming the internal hydrophobic cavity, and a long C-terminal tail. The measured volume of the Ag-LTP hydrophobic cavity is equal to ~800 A(3) , which is much larger than those of other plant LTP1s. Ag-LTP has weak antifungal activity and unpronounced lipid binding specificity but effectively binds plant hormone jasmonic acid. Our results afford further molecular insight into biological functions of LTP in plants. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd.
ID:1370 - (2015). Structural Insight into Specificity of Interactions between Nonconventional Three-finger Weak Toxin from Naja kaouthia (WTX) and Muscarinic Acetylcholine Receptors. J. Biol. Chem. 290 (39), 23616–30 [+]
Weak toxin from Naja kaouthia (WTX) belongs to the group of nonconventional "three-finger" snake neurotoxins. It irreversibly inhibits nicotinic acetylcholine receptors and allosterically interacts with muscarinic acetylcholine receptors (mAChRs). Using site-directed mutagenesis, NMR spectroscopy, and computer modeling, we investigated the recombinant mutant WTX analogue (rWTX) which, compared with the native toxin, has an additional N-terminal methionine residue. In comparison with the wild-type toxin, rWTX demonstrated an altered pharmacological profile, decreased binding of orthosteric antagonist N-methylscopolamine to human M1- and M2-mAChRs, and increased antagonist binding to M3-mAChR. Positively charged arginine residues located in the flexible loop II were found to be crucial for rWTX interactions with all types of mAChR. Computer modeling suggested that the rWTX loop II protrudes to the M1-mAChR allosteric ligand-binding site blocking the entrance to the orthosteric site. In contrast, toxin interacts with M3-mAChR by loop II without penetration into the allosteric site. Data obtained provide new structural insight into the target-specific allosteric regulation of mAChRs by "three-finger" snake neurotoxins.
ID:1394 - (2015). NMR Dynamics of Transmembrane and Intracellular Domains of p75NTR in Lipid-Protein Nanodiscs. Biophys. J. 109 (4), 772–82 [+]
P75NTR is a type I integral membrane protein that plays a key role in neurotrophin signaling. However, structural data for the receptor in various functional states are sparse and controversial. In this work, we studied the spatial structure and mobility of the transmembrane and intracellular parts of p75NTR, incorporated into lipid-protein nanodiscs of various sizes and compositions, by solution NMR spectroscopy. Our data reveal a high level of flexibility and disorder in the juxtamembrane chopper domain of p75NTR, which results in the motions of the receptor death domain being uncoupled from the motions of the transmembrane helix. Moreover, none of the intracellular domains of p75NTR demonstrated a propensity to interact with the membrane or to self-associate under the experimental conditions. The obtained data are discussed in the context of the receptor activation mechanism.
ID:1312 - (2015). Structure of Membrane-active Toxin from Crab Spider Heriaeus melloteei Suggests Parallel Evolution of Sodium Channel Gating Modifiers in Araneomorphae and Mygalomorphae. J. Biol. Chem. 290 (1), 492–504 [+]
We present a structural and functional study of a sodium channel activation inhibitor from crab spider venom. Hm-3 is an insecticidal peptide toxin consisting of 35 amino acid residues from the spider Heriaeus melloteei (Thomisidae). We produced Hm-3 recombinantly in Escherichia coli and determined its structure by NMR spectroscopy. Typical for spider toxins, Hm-3 was found to adopt the so-called "inhibitor cystine knot" or "knottin" fold stabilized by three disulfide bonds. Its molecule is amphiphilic with a hydrophobic ridge on the surface enriched in aromatic residues and surrounded by positive charges. Correspondingly, Hm-3 binds to both neutral and negatively charged lipid vesicles. Electrophysiological studies showed that at a concentration of 1 μm Hm-3 effectively inhibited a number of mammalian and insect sodium channels. Importantly, Hm-3 shifted the dependence of channel activation to more positive voltages. Moreover, the inhibition was voltage-dependent, and strong depolarizing prepulses attenuated Hm-3 activity. The toxin is therefore concluded to represent the first sodium channel gating modifier from an araneomorph spider and features a "membrane access" mechanism of action. Its amino acid sequence and position of the hydrophobic cluster are notably different from other known gating modifiers from spider venom, all of which are described from mygalomorph species. We hypothesize parallel evolution of inhibitor cystine knot toxins from Araneomorphae and Mygalomorphae suborders.
ID:1138 - (2014). Toll-like receptor 3 transmembrane domain is able to perform various homotypic interactions: An NMR structural study. FEBS Lett. , [+]
Toll-like receptors (TLRs) take part in both the innate and adaptive immune systems. The role of the transmembrane domain in TLR signaling is still elusive, while its importance for the TLR activation was clearly demonstrated. In the present study the ability of the TLR3 transmembrane domain to form dimers and trimers in detergent micelles was shown by solution NMR spectroscopy. Spatial structures and free energy magnitudes were determined for the TLR3 transmembrane domain in dimeric and trimeric states, and two possible surfaces that may be used for the helix-helix interaction by the full-length TLR3 were revealed.
ID:1107 - (2014). Heterologous expression and solution structure of defensin from lentil Lens culinaris. Biochem. Biophys. Res. Commun. 451 (2), 252–7 [+]
A new defensin Lc-def, isolated from germinated seeds of the lentil Lens culinaris, has molecular mass 5440.4Da and consists of 47 amino acid residues. Lc-def and its (15)N-labeled analog were overexpressed in Escherichia coli. Antimicrobial activity of the recombinant protein was examined, and its spatial structure, dynamics, and interaction with lipid vesicles were studied by NMR spectroscopy. It was shown that Lc-def is active against fungi, but does not inhibit the growth of Gram-positive and Gram-negative bacteria. The peptide is monomeric in aqueous solution and contains one α-helix and triple-stranded β-sheet, which form cysteine-stabilized αβ motif (CSαβ) previously found in other plant defensins. The sterically neighboring loop1 and loop3 protrude from the defensin core and demonstrate significant mobility on the μs-ms timescale. Lc-def does not bind to the zwitterionic lipid (POPC) vesicles but interacts with the partially anionic (POPC/DOPG, 7:3) membranes under low-salt conditions. The Lc-def antifungal activity might be mediated through electrostatic interaction with anionic lipid components of fungal membranes.
ID:1105 - (2014). Structural and functional characterization of alternative transmembrane domain conformations in VEGF receptor 2 activation. Structure 22 (8), 1077–89 [+]
Transmembrane signaling by receptor tyrosine kinases (RTKs) entails ligand-mediated dimerization and structural rearrangement of the extracellular domains. RTK activation also depends on the specific orientation of the transmembrane domain (TMD) helices, as suggested by pathogenic, constitutively active RTK mutants. Such mutant TMDs carry polar amino acids promoting stable transmembrane helix dimerization, which is essential for kinase activation. We investigated the effect of polar amino acids introduced into the TMD of vascular endothelial growth factor receptor 2, regulating blood vessel homeostasis. Two mutants showed constitutive kinase activity, suggesting that precise TMD orientation is mandatory for kinase activation. Nuclear magnetic resonance spectroscopy revealed that TMD helices in activated constructs were rotated by 180° relative to the interface of the wild-type conformation, confirming that ligand-mediated receptor activation indeed results from transmembrane helix rearrangement. A molecular dynamics simulation confirmed the transmembrane helix arrangement of wild-type and mutant TMDs revealed by nuclear magnetic resonance spectroscopy.
ID:1104 - (2014). Point mutations in dimerization motifs of the transmembrane domain stabilize active or inactive state of the EphA2 receptor tyrosine kinase. J. Biol. Chem. 289 (21), 14955–64 [+]
The EphA2 receptor tyrosine kinase plays a central role in the regulation of cell adhesion and guidance in many human tissues. The activation of EphA2 occurs after proper dimerization/oligomerization in the plasma membrane, which occurs with the participation of extracellular and cytoplasmic domains. Our study revealed that the isolated transmembrane domain (TMD) of EphA2 embedded into the lipid bicelle dimerized via the heptad repeat motif L(535)X3G(539)X2A(542)X3V(546)X2L(549) rather than through the alternative glycine zipper motif A(536)X3G(540)X3G(544) (typical for TMD dimerization in many proteins). To evaluate the significance of TMD interactions for full-length EphA2, we substituted key residues in the heptad repeat motif (HR variant: G539I, A542I, G553I) or in the glycine zipper motif (GZ variant: G540I, G544I) and expressed YFP-tagged EphA2 (WT, HR, and GZ variants) in HEK293T cells. Confocal microscopy revealed a similar distribution of all EphA2-YFP variants in cells. The expression of EphA2-YFP variants and their kinase activity (phosphorylation of Tyr(588) and/or Tyr(594)) and ephrin-A3 binding were analyzed with flow cytometry on a single cell basis. Activation of any EphA2 variant is found to occur even without ephrin stimulation when the EphA2 content in cells is sufficiently high. Ephrin-A3 binding is not affected in mutant variants. Mutations in the TMD have a significant effect on EphA2 activity. Both ligand-dependent and ligand-independent activities are enhanced for the HR variant and reduced for the GZ variant compared with the WT. These findings allow us to suggest TMD dimerization switching between the heptad repeat and glycine zipper motifs, corresponding to inactive and active receptor states, respectively, as a mechanism underlying EphA2 signal transduction.
ID:1139 - (2014). Structural similarity between defense peptide from wheat and scorpion neurotoxin permits rational functional design. J. Biol. Chem. 289 (20), 14331–40 [+]
In this study, we present the spatial structure of the wheat antimicrobial peptide (AMP) Tk-AMP-X2 studied using NMR spectroscopy. This peptide was found to adopt a disulfide-stabilized α-helical hairpin fold and therefore belongs to the α-hairpinin family of plant defense peptides. Based on Tk-AMP-X2 structural similarity to cone snail and scorpion potassium channel blockers, a mutant molecule, Tk-hefu, was engineered by incorporating the functionally important residues from κ-hefutoxin 1 onto the Tk-AMP-X2 scaffold. The designed peptide contained the so-called essential dyad of amino acid residues significant for channel-blocking activity. Electrophysiological studies showed that although the parent peptide Tk-AMP-X2 did not present any activity against potassium channels, Tk-hefu blocked Kv1.3 channels with similar potency (IC50 ∼ 35 μm) to κ-hefutoxin 1 (IC50 ∼ 40 μm). We conclude that α-hairpinins are attractive in their simplicity as structural templates, which may be used for functional engineering and drug design.
ID:1103 - (2013). NMR-based approach to measure the free energy of transmembrane helix-helix interactions. Biochim. Biophys. Acta 1838 (1PB), 164–172 [+]
Knowledge of the energetic parameters of transmembrane helix-helix interactions is necessary for the establishment of a structure-energy relationship for α-helical membrane domains. A number of techniques have been developed to measure the free energies of dimerization and oligomerization of transmembrane α-helices, and all of these have their advantages and drawbacks. In this study we propose a methodology to determine the magnitudes of the free energy of interactions between transmembrane helices in detergent micelles. The suggested approach employs solution nuclear magnetic resonance (NMR) spectroscopy to determine the population of the oligomeric states of the transmembrane domains and introduces a new formalism to describe the oligomerization equilibrium, which is based on the assumption that both the dimerization of the transmembrane domains and the dissociation of the dimer can occur only upon the collision of detergent micelles. The technique has three major advantages compared with other existing approaches: it may be used to analyze both weak and relatively strong dimerization/oligomerization processes, it works well for the analysis of complex equilibria, e.g. when monomer, dimer and high-order oligomer populations are simultaneously present in the solution, and it can simultaneously yield both structural and energetic characteristics of the helix-helix interaction under study. The proposed methodology was applied to investigate the oligomerization process of transmembrane domains of fibroblast growth factor receptor 3 (FGFR3) and vascular endothelium growth factor receptor 2 (VEGFR2), and allowed the measurement of the free energy of dimerization of both of these objects. In addition the proposed method was able to describe the multi-state oligomerization process of the VEGFR2 transmembrane domain.
ID:967 - (2013). Structural insights into the proton pumping by unusual proteorhodopsin from nonmarine bacteria. Proc. Natl. Acad. Sci. U.S.A. 110 (31), 12631–6 [+]
Light-driven proton pumps are present in many organisms. Here, we present a high-resolution structure of a proteorhodopsin from a permafrost bacterium, Exiguobacterium sibiricum rhodopsin (ESR). Contrary to the proton pumps of known structure, ESR possesses three unique features. First, ESR's proton donor is a lysine side chain that is situated very close to the bulk solvent. Second, the α-helical structure in the middle of the helix F is replaced by 3(10)- and π-helix-like elements that are stabilized by the Trp-154 and Asn-224 side chains. This feature is characteristic for the proteorhodopsin family of proteins. Third, the proton release region is connected to the bulk solvent by a chain of water molecules already in the ground state. Despite these peculiarities, the positions of water molecule and amino acid side chains in the immediate Schiff base vicinity are very well conserved. These features make ESR a very unusual proton pump. The presented structure sheds light on the large family of proteorhodopsins, for which structural information was not available previously.
ID:1260 - (2013). Peptaibol antiamoebin I: spatial structure, backbone dynamics, interaction with bicelles and lipid-protein nanodiscs, and pore formation in context of barrel-stave model. Chem. Biodivers. 10 (5), 838–63 [+]
Antiamoebin I (Aam-I) is a membrane-active peptaibol antibiotic isolated from fungal species belonging to the genera Cephalosporium, Emericellopsis, Gliocladium, and Stilbella. In comparison with other 16-amino acid-residue peptaibols, e.g., zervamicin IIB (Zrv-IIB), Aam-I possesses relatively weak biological and channel-forming activities. In MeOH solution, Aam-I demonstrates fast cooperative transitions between right-handed and left-handed helical conformation of the N-terminal (1-8) region. We studied Aam-I spatial structure and backbone dynamics in the membrane-mimicking environment (DMPC/DHPC bicelles)(1) ) by heteronuclear (1) H,(13) C,(15) N-NMR spectroscopy. Interaction with the bicelles stabilizes the Aam-I right-handed helical conformation retaining significant intramolecular mobility on the ms-μs time scale. Extensive ms-μs dynamics were also detected in the DPC and DHPC micelles and DOPG nanodiscs. In contrast, Zrv-IIB in the DPC micelles demonstrates appreciably lesser mobility on the μs-ms time scale. Titration with Mn(2+) and 16-doxylstearate paramagnetic probes revealed Aam-I binding to the bicelle surface with the N-terminus slightly immersed into hydrocarbon region. Fluctuations of the Aam-I helix between surface-bound and transmembrane (TM) state were observed in the nanodisc membranes formed from the short-chain (diC12 : 0) DLPC/DLPG lipids. All the obtained experimental data are in agreement with the barrel-stave model of TM pore formation, similarly to the mechanism proposed for Zrv-IIB and other peptaibols. The observed extensive intramolecular dynamics explains the relatively low activity of Aam-I.
ID:978 - (2013). Lipid-protein nanodiscs promote in vitro folding of transmembrane domains of multi-helical and multimeric membrane proteins. Biochim. Biophys. Acta 1828 (2), 776–84 [+]
Production of helical integral membrane proteins (IMPs) in a folded state is a necessary prerequisite for their functional and structural studies. In many cases large-scale expression of IMPs in cell-based and cell-free systems results in misfolded proteins, which should be refolded in vitro. Here using examples of the bacteriorhodopsin ESR from Exiguobacterium sibiricum and full-length homotetrameric K(+) channel KcsA from Streptomyces lividans we found that the efficient in vitro folding of the transmembrane domains of the polytopic and multimeric IMPs could be achieved during the protein encapsulation into the reconstructed high-density lipoprotein particles, also known as lipid-protein nanodiscs. In this case the self-assembly of the IMP/nanodisc complexes from a mixture containing apolipoprotein, lipids and the partially denatured protein solubilized in a harsh detergent induces the folding of the transmembrane domains. The obtained folding yields showed significant dependence on the properties of lipids used for nanodisc formation. The largest recovery of the spectroscopically active ESR (~60%) from the sodium dodecyl sulfate (SDS) was achieved in the nanodiscs containing anionic saturated lipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPG) and was approximately twice lower in the zwitterionic DMPC lipid. The reassembly of tetrameric KcsA from the acid-dissociated monomer solubilized in SDS was the most efficient (~80%) in the nanodiscs containing zwitterionic unsaturated lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). The charged and saturated lipids provided lower tetramer quantities, and the lowest yield (<20%) was observed in DMPC. The overall yield of the ESR and KcsA folding was mainly restricted by the efficiency of the protein encapsulation into the nanodiscs.
ID:802 - (2012). Recombinant expression and solution structure of antimicrobial peptide aurelin from jellyfish Aurelia aurita. Biochem. Biophys. Res. Commun. 429 (1-2), 63–9 [+]
Aurelin is a 40-residue cationic antimicrobial peptide isolated from the mezoglea of a scyphoid jellyfish Aurelia aurita. Aurelin and its (15)N-labeled analogue were overexpressed in Escherichia coli and purified. Antimicrobial activity of the recombinant peptide was examined, and its spatial structure was studied by NMR spectroscopy. Aurelin represents a compact globule, enclosing one 3(10)-helix and two α-helical regions cross-linked by three disulfide bonds. The peptide binds to anionic lipid (POPC/DOPG, 3:1) vesicles even at physiological salt concentration, it does not interact with zwitterionic (POPC) vesicles and interacts with the DPC micelle surface with moderate affinity via two α-helical regions. Although aurelin shows structural homology to the BgK and ShK toxins of sea anemones, its surface does not possess the "functional dyad" required for the high-affinity interaction with the K(+)-channels. The obtained data permit to correlate the modest antibacterial properties and membrane activity of aurelin.
ID:977 - (2012). Structural and thermodynamic insight into the process of "weak" dimerization of the ErbB4 transmembrane domain by solution NMR. Biochim. Biophys. Acta 1818 (9), 2158–70 [+]
Specific helix-helix interactions between the single-span transmembrane domains of receptor tyrosine kinases are believed to be important for their lateral dimerization and signal transduction. Establishing structure-function relationships requires precise structural-dynamic information about this class of biologically significant bitopic membrane proteins. ErbB4 is a ubiquitously expressed member of the HER/ErbB family of growth factor receptor tyrosine kinases that is essential for the normal development of various adult and fetal human tissues and plays a role in the pathobiology of the organism. The dimerization of the ErbB4 transmembrane domain in membrane-mimicking lipid bicelles was investigated by solution NMR. In a bicellar DMPC/DHPC environment, the ErbB4 membrane-spanning α-helices (651-678)(2) form a right-handed parallel dimer through the N-terminal double GG4-like motif A(655)GxxGG(660) in a fashion that is believed to permit proper kinase domain activation. During helix association, the dimer subunits undergo a structural adjustment (slight bending) with the formation of a network of inter-monomeric polar contacts. The quantitative analysis of the observed monomer-dimer equilibrium provides insights into the kinetics and thermodynamics of the folding process of the helical transmembrane domain in the model environment that may be directly relevant to the process that occurs in biological membranes. The lipid bicelles occupied by a single ErbB4 transmembrane domain behave as a true ("ideal") solvent for the peptide, while multiply occupied bicelles are more similar to the ordered lipid microdomains of cellular membranes and appear to provide substantial entropic enhancement of the weak helix-helix interactions, which may be critical for membrane protein activity.
ID:731 - (2012). Lignan from thyme possessing inhibitory effect on ASIC3 current. J. Biol. Chem. , [+]
Novel compound was identified in acidic extract of Thymus armeniacus collected in the Lake Sevan region of Armenia. This compound, named sevanol, to our knowledge is the first low molecular weight natural molecule that has a reversible inhibition effect both on transient and sustained current of human ASIC3 channels expressed in Xenopus laevis oocytes. Sevanol completely blocked the transient component (IC50 353+/-23 μM) and partially (~45%) inhibited the amplitude of sustained component (IC50 of 234+/-53 μM). Other types of ASICs channels were intact to sevanol application except ASIC1a that showed more than 6 times less affinity to it as compared with inhibitory action on ASIC3 channel. To elucidate sevanol structure the set of NMR spectra in two solvents: d6-DMSO and D2O was collected and the complete chemical structure was confirmed by LC-ESI+-MS fragmentation. This compound is a new lignan built up of epiphyllic acid and two isocytril esters in positions 9, 10. In vivo administration of sevanol (1-10 mg/kg) significantly reversed of thermal hyperalgesia induced by complete Freund adjuvant (CFA) injection and reduced response to acid in writhing test. Thus we assume the probable considerable role of sevanol in known analgesic and anti-inflammatory properties of thyme.
ID:725 - (2012). Dimeric structure of transmembrane domain of amyloid precursor protein in micellar environment. FEBS Lett. 586 (12), 1687–92 [+]
Some pathogenic mutations associated with Alzheimer's disease are thought to affect structural-dynamic properties and the lateral dimerization of amyloid precursor protein (APP) in neuron membrane. Dimeric structure of APP transmembrane fragment Gln(686)-Lys(726) was determined in membrane-mimicking dodecylphosphocholine micelles using high-resolution NMR spectroscopy. The APP membrane-spanning α-helix Lys(699)-Lys(724) self-associates in a left-handed parallel dimer through extended heptad repeat motif I(702)X(3)M(706)X(2)G(709)X(3)A(713)X(2)I(716)X(3)I(720)X(2)I(723), whereas the juxtamembrane region Gln(686)-Val(695) constitutes the nascent helix, also sensing the dimerization. The dimerization mechanism of APP transmembrane domain has been described at atomic resolution for the first time and is important for understanding molecular events of APP sequential proteolytical cleavage resulting in amyloid-β peptide.
ID:749 - (2011). Novel lynx spider toxin shares common molecular architecture with defense peptides from frog skin. FEBS J. 278 (22), 4382–93 [+]
A unique 30-residue cationic peptide oxyopinin 4a (Oxt 4a) was identified in the venom of the lynx spider Oxyopes takobius (Oxyopidae). Oxt 4a contains a single N-terminally located disulfide bond, Cys4-Cys10, and is structurally different from any spider toxin studied so far. According to NMR findings, the peptide is disordered in water, but assumes a peculiar torpedo-like structure in detergent micelles. It features a C-terminal amphipathic α-helical segment (body; residues 12-25) and an N-terminal disulfide-stabilized loop (head; residues 1-11), and has an unusually high density of positive charge in the head region. Synthetic Oxt 4a was produced and shown to possess strong and broad-spectrum cytolytic and antimicrobial activity. cDNA cloning showed that the peptide is synthesized in the form of a conventional prepropeptide with an acidic prosequence. Unlike other arachnid toxins, Oxt 4a exhibits striking similarity with defense peptides from the skin of ranid frogs that contain the so-called Rana-box motif (a C-terminal disulfide-enclosed loop). Parallelism or convergence is apparent on several levels: the structure, function and biosynthesis of a lynx spider toxin are mirrored by those of Rana-box peptides from frogs. DATABASE: The protein sequence of oxyopinin 4a (Oxt 4a) has been submitted to the UniProt Knowledgebase (UniProtKB) under the accession number P86350. The coordinates and chemical shifts of Oxt 4a in complex with dodecylphosphocholine micelles have been deposited in the Protein Data Bank and Biological Magnetic Resonance Bank under the accession codes 2L3I and 17194, respectively. The nucleotide sequence encoding Oxt 4a has been submitted to the EMBL Nucleotide Sequence Database under the accession number FN997582.
ID:546 - (2011). Molecular mechanism of action of β-hairpin antimicrobial peptide arenicin: oligomeric structure in dodecylphosphocholine micelles and pore formation in planar lipid bilayers. Biochemistry 50 (28), 6255–65 [+]
The membrane-active, cationic, β-hairpin peptide, arenicin, isolated from marine polychaeta Arenicola marina exhibits a broad spectrum of antimicrobial activity. The peptide in aqueous solution adopts the significantly twisted β-hairpin conformation without pronounced amphipathicity. To assess the mechanism of arenicin action, the spatial structure and backbone dynamics of the peptide in membrane-mimicking media and its pore-forming activity in planar lipid bilayers were studied. The spatial structure of the asymmetric arenicin dimer stabilized by parallel association of N-terminal strands of two β-hairpins was determined using triple-resonance nuclear magnetic resonance (NMR) spectroscopy in dodecylphosphocholine (DPC) micelles. Interaction of arenicin with micelles and its oligomerization significantly decreased the right-handed twist of the β-hairpin, increased its amphipathicity, and led to stabilization of the peptide backbone on a picosecond to nanosecond time scale. Relaxation enhancement induced by water-soluble (Mn(2+)) and lipid-soluble (16-doxylstearate) paramagnetic probes pointed to the dimer transmembrane arrangement. Qualitative NMR and circular dichroism study of arenicin-2 in mixed DPC/1,2-dioleoyl-sn-glycero-3-phosphoglycerol bicelles, sodium dodecyl sulfate micelles, and lipid vesicles confirmed that a similar dimeric assembly of the peptide was retained in membrane-mimicking systems containing negatively charged lipids and detergents. Arenicin-induced conductance was dependent on the lipid composition of the membrane. Arenicin low-conductivity pores were detected in the phosphatidylethanolamine-containing lipid mixture, whereas the high-conductivity pores were observed in an exclusively anionic lipid system. The measured conductivity levels agreed with the model in which arenicin antimicrobial activity was mediated by the formation of toroidal pores assembled of two, three, or four β-structural peptide dimers and lipid molecules. The structural transitions involved in arenicin membrane-disruptive action are discussed.
ID:535 - (2010). Isolation, structure elucidation, and synergistic antibacterial activity of a novel two-component lantibiotic lichenicidin from Bacillus licheniformis VK21. Biochemistry 49 (30), 6462–72 [+]
A novel synergetic lantibiotic pair, Lchalpha(3249.51 Da) and Lchbeta(3019.36 Da), termed lichenicidin VK21, was isolated from the producer strain Bacillus licheniformis VK21. Chemical and spatial structures of Lchalphaand Lchbeta were determined. Each peptide contains 31 amino acid residues linked by 4 intramolecular thioether bridges and the N-terminal 2-oxobutyryl group. Spatial structures of Lchalpha and Lchbetawere studied by NMR spectroscopy in methanol solution. Lchalpha peptide displays structural homology with mersacidin-like lantibiotics and involves relatively well-structured N- and C-terminal domains connected by a flexible loop stabilized by thioether bridge Ala11-S-Ala21. In contrast, the Lchbetapeptide represents prolonged hydrophobic alpha-helix flanked with more flexible N- and C-terminal domains. A lantibiotic cluster of the Bacillus licheniformis VK21 genome which comprises the structural genes, lchA1 and lchA2, encoding the lantibiotics precursors, as well as the gene of a modifying enzyme lchM1, was amplified and sequenced. The mature peptides, Lchalphaand Lchbetainteract synergistically to possess antibiotic activity against Gram-positive bacteria within a nanomolar concentration range, though the individual peptides were shown to be active at micromolar concentrations. Our results afford molecular insight into mechanism of lichenicidin VK21 action.
ID:359 - (2010). Spatial Structure of the Transmembrane Domain Heterodimer of ErbB1 and ErbB2 Receptor Tyrosine Kinases. J. Mol. Biol. 400 (2), 231–243 [+]
Growth factor receptor tyrosine kinases of the ErbB family play a significant role in vital cellular processes and various cancers. During signal transduction across plasma membrane, ErbB receptors are involved in lateral homodimerization and heterodimerization with proper assembly of their extracellular single-span transmembrane (TM) and cytoplasmic domains. The ErbB1/ErbB2 heterodimer appears to be the strongest and most potent inducer of cellular transformation and mitogenic signaling compared to other ErbB homodimers and heterodimers. Spatial structure of the heterodimeric complex formed by TM domains of ErbB1 and ErbB2 receptors embedded into lipid bicelles was obtained by solution NMR. The ErbB1 and ErbB2 TM domains associate in a right-handed alpha-helical bundle through their N-terminal double GG4-like motif T(648)G(649)X(2)G(652)A(653) and glycine zipper motif T(652)X(3)S(656)X(3)G(660), respectively. The described heterodimer conformation is believed to support the juxtamembrane and kinase domain configuration corresponding to the receptor active state. The capability for multiple polar interactions, along with hydrogen bonding between TM segments, correlates with the observed highest affinity of the ErbB1/ErbB2 heterodimer, implying an important contribution of the TM helix-helix interaction to signal transduction.
ID:346 - (2010). Left-handed dimer of EphA2 transmembrane domain: Helix packing diversity among receptor tyrosine kinases. Biophys. J. 98 (5), 881–9 [+]
The Eph receptor tyrosine kinases and their membrane-bound ephrin ligands control a diverse array of cell-cell interactions in the developing and adult organisms. During signal transduction across plasma membrane, Eph receptors, like other receptor tyrosine kinases, are involved in lateral dimerization and subsequent oligomerization presumably with proper assembly of their single-span transmembrane domains. Spatial structure of dimeric transmembrane domain of EphA2 receptor embedded into lipid bicelle was obtained by solution NMR, showing a left-handed parallel packing of the transmembrane helices (535-559)(2). The helices interact through the extended heptad repeat motif L(535)X(3)G(539)X(2)A(542)X(3)V(546)X(2)L(549) assisted by intermolecular stacking interactions of aromatic rings of (FF(557))(2), whereas the characteristic tandem GG4-like motif A(536)X(3)G(540)X(3)G(544) is not used, enabling another mode of helix-helix association. Importantly, a similar motif AX(3)GX(3)G as was found is responsible for right-handed dimerization of transmembrane domain of the EphA1 receptor. These findings serve as an instructive example of the diversity of transmembrane domain formation within the same family of protein kinases and seem to favor the assumption that the so-called rotation-coupled activation mechanism may take place during the Eph receptor signaling. A possible role of membrane lipid rafts in relation to Eph transmembrane domain oligomerization and Eph signal transduction was also discussed.
ID:320 - (2009). Bacterial synthesis, purification, and solubilization of membrane protein KCNE3, a regulator of voltage-gated potassium channels. Biochemistry Mosc. 74 (12), 1344–9 [+]
Описан эффективный способ получения мембранного белка KCNE3, а также его изотопно-меченых производных (15N-, 13C-), в количествах, достаточных для проведения структурно-функциональных исследований. Очищенный белковый препарат в составе мицелл различных детергентов охарактеризован методами динамического светорассеяния, КД-спектроскопии и ЯМР-спектроскопии. Показано, что в мицеллах DPC/LDAO белок находится в мономерной форме и принимает преимущественно альфа-спиральную конформацию. Наличие кросс-пиков от всех глицинов в 15N-HSQC–спектре ЯМР, а также относительно небольшая ширина линий (~20 Гц) подтверждают высокое качество полученного образца и возможность получения структурно-динамической информации о KCNE3 методом гетероядерной спектроскопии ЯМР высокого разрешения.
ID:273 - (2009). Loop 3 of short neurotoxin II is an additional interaction site with membrane-bound nicotinic acetylcholine receptor as detected by solid-state NMR spectroscopy. J. Mol. Biol. 390 (4), 662–71 [+]
The contact area of neurotoxin II from Naja naja oxiana when interacting with the membrane-bound nicotinic acetylcholine receptor from Torpedo californica was determined by solid-state, magic-angle spinning NMR spectroscopy. For this purpose, the carbon signals for more than 90% of the residues of the bound neurotoxin were assigned. Differences between the solution and solid-state chemical shifts of the free and bound form of the toxin are confined to distinct surface regions. Loop II of the short toxin was identified as the main interaction site. In addition, loop III of neurotoxin II shows several strong responses defining an additional interaction site. A comparison with the structures of alpha-cobratoxin bound to the acetylcholine-binding protein from snail species Lymnaea stagnalis and Aplysia californica, and of alpha-bungarotoxin bound to an extracellular domain of an alpha-subunit of the receptor reveals different contact areas for long and short alpha-neurotoxins.
ID:354 - (2009). Lipid-protein nanodiscs: possible application in high-resolution NMR investigations of membrane proteins and membrane-active peptides. Biochemistry Mosc. 74 (7), 756–65 [+]
High-resolution NMR is shown to be applicable for investigation of membrane proteins and membrane-active peptides embedded into lipid-protein nanodiscs (LPNs). (15)N-Labeled K+-channel from Streptomyces lividans (KcsA) and the antibiotic antiamoebin I from Emericellopsis minima (Aam-I) were embedded in LPNs of different lipid composition. Formation of stable complexes undergoing isotropic motion in solution was confirmed by size-exclusion chromatography and (31)P-NMR spectroscopy. The 2D 1H-(15)N-correlation spectra were recorded for KcsA in the complex with LPN containing DMPC and for Aam-I in LPNs based on DOPG, DLPC, DMPC, and POPC. The spectra recorded were compared with those in detergent-containing micelles and small bicelles commonly used in high-resolution NMR spectroscopy of membrane proteins. The spectra recorded in LPN environments demonstrated similar signal dispersion but significantly increased (1)H(N) line width. The spectra of Aam-I embedded in LPNs containing phosphatidylcholine showed significant selective line broadening, thus suggesting exchange process(es) between several membrane-bound states of the peptide. (15)N relaxation rates were measured to obtain the effective rotational correlation time of the Aam-I molecule. The obtained value (approximately 40 nsec at 45 degrees C) is indicative of additional peptide motions within the Aam-I/LPN complex.
ID:353 - (2009). Recombinant Kv channels at the membrane of Escherichia coli bind specifically agitoxin2. J Neuroimmune Pharmacol 4 (1), 83–91 [+]
Potassium voltage-gated channels (Kv) are considered as molecular targets in a number of serious neuronal, immune, and cardiac disorders. Search for efficient low-molecular weight modulators of Kv channel function provides a basis for the development of an appropriate therapy for various Kv-mediated diseases. We report here on a new bacterial cell-based system, which is suitable for study of interactions between ligands and ligand-binding sites of eukaryotic Kv1.3 and Kv1.1 channels. To create this system, high-level expression of KcsA-Kv1.3 and KcsA-Kv1.1 hybrid proteins (ligand-binding sites of Kv1.3 or Kv1.1 fused with prokaryotic KcsA potassium channel) was achieved in the plasma membrane of Escherichia coli. An efficient procedure of E. coli conversion to intact spheroplasts was developed. We demonstrate that fluorescently labeled agitoxin 2 binds specifically to high-affinity and lower-affinity sites of KcsA-Kv1.3 and KcsA-Kv1.1, respectively, at the membrane of spheroplasts. Number of binding sites per cell is estimated to be (1.0 +/- 0.6) x 10(5) and (0.3 +/- 0.2) x 10(5) for KcsA-Kv1.3- and KcsA-Kv1.1-presenting cells, respectively, that allows reliable detection of ligand-receptor interactions by confocal laser scanning microscopy. This bacterial cell-based system is intended for screening of ligands to membrane-embedded pharmaceutical targets.
ID:786 - (2009). Adaptation of a membrane-active peptide to heterogeneous environment. I. Structural plasticity of the peptide. The journal of physical chemistry. B 113 (4), 1107–19 [+]
В статье приводится детальное описание различных факторов, определяющих процесс взаимодействия мембрано-активного пептида (неспецифический переносчик—пенетратин) с липидными бислоями разного состава. К ключевым факторам следует отнести: конформационную подвижность пептида, способность аминокислотных остатков образовывать специфические контакты с другими остатками пептида, а также полярными головками липидов.
ID:125 - (2009). Adaptation of a membrane-active peptide to heterogeneous environment. II. The role of mosaic nature of the membrane surface. The journal of physical chemistry. B 113 (4), 1120–6 [+]
В статье постулируется мозаичная гидрофобно-гдрофильная организация поверхности липидной мембраны. Рассматривается влияние гетерогенности полярных свойств границы раздела вода-липиды на процесс связывания мембрано-активных агентов (на примере неспецифического пептидного переносчика — пенетратина).
ID:126 - (2009). Structure elucidation of dimeric transmembrane domains of bitopic proteins. Cell Adh Migr 4 (2), 284–98 [+]
The interaction between transmembrane helices is of great interest because it directly determines biological activity of a membrane protein. Either destroying or enhancing such interactions can result in many diseases related to dysfunction of different tissues in human body. One much studied form of membrane proteins known as bitopic protein is a dimer containing two membrane-spanning helices associating laterally. Establishing structure-function relationship as well as rational design of new types of drugs targeting membrane proteins requires precise structural information about this class of objects. At present time, to investigate spatial structure and internal dynamics of such transmembrane helical dimers, several strategies were developed based mainly on a combination of NMR spectroscopy, optical spectroscopy, protein engineering and molecular modeling. These approaches were successfully applied to homo- and heterodimeric transmembrane fragments of several bitopic proteins, which play important roles in normal and in pathological conditions of human organism.
ID:1047 - (2008). Molecular insight into mechanism of antimicrobial action of the beta-hairpin peptide arenicin: specific oligomerization in detergent micelles. Biopolymers 89 (5), 455–64 [+]
Arenicins are 21-residue cationic antimicrobial peptides isolated from marine polychaeta Arenicola marina. The peptides exhibit potent broad-spectrum antimicrobial activity. In water solution arenicin-2 adopts a beta-hairpin conformation, stabilized by one disulfide and nine hydrogen bonds. To determine the propensity for the peptide oligomerization in membrane mimetic systems, the recombinant arenicin-2 was overexpressed as a fused form in Escherichia coli. The arenicin-2 oligomerization and intermolecular packing in membrane mimicking environment were investigated using high-resolution NMR spectroscopy. The present studies show that arenicin-2 preserves a beta-hairpin structure and forms asymmetric dimers upon incorporation into the dodecylphosphocholine micelle. Two monomers of arenicin-2 are aligned parallel to each other by the N-terminal strands of the beta-hairpin (CN upward arrow upward arrowNC type of association). Polyacrylamide gel electrophoresis analysis indicated that in environment of anionic SDS micelles the arenicin-2 might undergo further oligomerization and form tetramers. Our results afford further molecular insight into possible mechanism of antimicrobial action of arenicins.
ID:414 - (2008). Three-dimensional structure/hydrophobicity of latarcins specifies their mode of membrane activity. Biochemistry 47 (11), 3525–33 [+]
Latarcins, linear peptides from the Lachesana tarabaevi spider venom, exhibit a broad-spectrum antimicrobial activity, likely acting on the bacterial cytoplasmic membrane. We study their spatial structures and interaction with model membranes by a combination of experimental and theoretical methods to reveal the structure-activity relationship. In this work, a 26 amino acid peptide, Ltc1, was investigated. Its spatial structure in detergent micelles was determined by (1)H nuclear magnetic resonance (NMR) and refined by Monte Carlo simulations in an implicit water-octanol slab. The Ltc1 molecule was found to form a straight uninterrupted amphiphilic helix comprising 8-23 residues. A dye-leakage fluorescent assay and (31)P NMR spectroscopy established that the peptide does not induce the release of fluorescent marker nor deteriorate the bilayer structure of the membranes. The voltage-clamp technique showed that Ltc1 induces the current fluctuations through planar membranes when the sign of the applied potential coincides with the one across the bacterial inner membrane. This implies that Ltc1 acts on the membranes via a specific mechanism, which is different from the carpet mode demonstrated by another latarcin, Ltc2a, featuring a helix-hinge-helix structure with a hydrophobicity gradient along the peptide chain. In contrast, the hydrophobic surface of the Ltc1 helix is narrow-shaped and extends with no gradient along the axis. We have also disclosed a number of peptides, structurally homologous to Ltc1 and exhibiting similar membrane activity. This indicates that the hydrophobic pattern of the Ltc1 helix and related antimicrobial peptides specifies their activity mechanism. The latter assumes the formation of variable-sized lesions, which depend upon the potential across the membrane.
ID:315 - (2008). Spatial structure of the dimeric transmembrane domain of the growth factor receptor ErbB2 presumably corresponding to the receptor active state. J. Biol. Chem. 283 (11), 6950–6 [+]
Proper lateral dimerization of the transmembrane domains of receptor tyrosine kinases is required for biochemical signal transduction across the plasma membrane. The spatial structure of the dimeric transmembrane domain of the growth factor receptor ErbB2 embedded into lipid bicelles was obtained by solution NMR, followed by molecular dynamics relaxation in an explicit lipid bilayer. ErbB2 transmembrane segments associate in a right-handed alpha-helical bundle through the N-terminal tandem GG4-like motif Thr652-X3-Ser656-X3-Gly660, providing an explanation for the pathogenic power of some oncogenic mutations.
ID:314 - (2008). Lipid-protein nanoscale bilayers: a versatile medium for NMR investigations of membrane proteins and membrane-active peptides. J. Am. Chem. Soc. 130 (7), 2140–1 ID:356
- (2007). Specificity of helix packing in transmembrane dimer of the cell death factor BNIP3: a molecular modeling study. Proteins 69 (2), 309–25 [+]
Предложен вычислительный метод предсказания пространственной структуры димеров трансмембранных альфа-спиралей. Подход основан на применении модели неявно заданной мембраны и конформационного поиска методом Монте-Карло в пространстве двугранных углов пептидов. Эффективность метода продемонстрирована на примере трансмембранного домена проапоптотического митохондриального белка BNIP3.
ID:124 - (2007). Recombinant expression, synthesis, purification, and solution structure of arenicin. Biochem. Biophys. Res. Commun. 360 (1), 156–62 [+]
Arenicins are 21-residue cationic antimicrobial peptides, isolated from marine polychaeta Arenicola marina. In order to determine a high-resolution three-dimensional structure of arenicin-2, the recombinant peptide was overexpressed as a fused form in Escherichia coli. Both arenicin isoforms were synthesized using the Fmoc-based solid-phase strategy. Recombinant and synthetic arenicins were purified, and their antimicrobial and spectroscopic properties were analyzed. NMR investigation shows that in water solution arenicin-2 displays a prolonged beta-hairpin, formed by two antiparallel beta-strands and stabilized by one disulfide and nine hydrogen bonds. A significant right-handed twist in the beta-sheet is deprived the peptide surface of amphipathicity. CD spectroscopic analysis indicates that arenicin-2 binds to the SDS and DPC micelles, and conformation of the peptide is significantly changed upon binding. Arenicin strongly binds to anionic lipid (POPE/POPG) vesicles in contrast with zwitterionic (POPC) ones. These results suggest that arenicins are membrane active peptides and point to possible mechanism of their selectivity toward bacterial cells.
ID:419 - (2007). Antiamoebin I in methanol solution: rapid exchange between right-handed and left-handed 3(10)-helical conformations. Chem. Biodivers. 4 (6), 1219–42 [+]
Antiamoebin I (Aam-I) is a membrane-active peptaibol antibiotic isolated from fungal species belonging to the genera Cephalosporium, Emericellopsis, Gliocladium, and Stilbella. Antiamoebin I has the amino acid sequence: Ac-Phe(1)-Aib-Aib-Aib-Iva-Gly-Leu-Aib(8)-Aib-Hyp-Gln-Iva-Hyp-Aib-Pro-Phl(16). By using the uniformly (13)C,(15)N-labeled sample of Aam-I, the set of conformationally dependent J couplings and (3h)J(NC) couplings through H-bonds were measured. Analysis of these data along with the data on magnetic nonequivalence of the (13)C(beta) nuclei (Deltadelta((13)C(beta))) in Aib and Iva residues allowed us to draw the univocal conclusion that the N-terminal part (Phe(1)-Gly(6)) of Aam-I in MeOH solution is in fast exchange between the right-handed and left-handed 3(10)-helical conformations, with an approximately equal population of both states. An additional conformational exchange process was found at the Aib(8) residue. The (15)N-NMR-relaxation and CD-spectroscopy measurements confirmed these findings. Molecular modeling and Monte Carlo simulations revealed that both exchange processes are correlated and coupled with significant hinge-bending motions around the Aib(8) residue. Our results explain relatively low activity of Aam-I with respect to other 15-amino acid residue peptaibols (for example, zervamicin) in functional and biological tests. The high dynamic 'propensity' possibly prevents both initial binding of the antiamoebin to the membrane and subsequent formation of stable ionic channels according to the barrel-stave mechanism.
ID:418 - (2007). Method to assess packing quality of transmembrane alpha-helices in proteins. 1. Parametrization using structural data. Journal of chemical information and modeling 47 (3), 1150–62 [+]
Integral membrane proteins (MPs) are pharmaceutical targets of exceptional importance. Modern methods of three-dimensional protein structure determination often fail to supply the fast growing field of structure-based drug design with the requested MPs' structures. That is why computational modeling techniques gain a special importance for these objects. Among the principal difficulties limiting application of these methods is the low quality of the MPs' models built in silico. In this series of two papers we present a computational approach to the assessment of the packing "quality" of transmembrane (TM) alpha-helical domains in proteins. The method is based on the concept of protein environment classes, whereby each amino acid residue is described in terms of its environment polarity and accessibility to the membrane. In the first paper we analyze a nonredundant set of 26 TM alpha-helical domains and compute the residues' propensities to five predefined classes of membrane-protein environments. Here we evaluate the proposed approach only by various test sets, cross-validation protocols and ability of the method to delimit the crystal structure of visual rhodopsin, and a number of its erroneous theoretical models. More advanced validation of the method is given in the second article of this series. We assume that the developed "membrane score" method will be helpful in optimizing computer models of TM domains of MPs, especially G-protein coupled receptors.
ID:1 - (2007). Method to assess packing quality of transmembrane alpha-helices in proteins. 2. Validation by "correct vs misleading" test. Journal of chemical information and modeling 47 (3), 1163–70 [+]
We describe a set of tests designed to check the ability of the new "membrane score" method (see the first paper of this series) to assess the packing quality of transmembrane (TM) alpha-helical domains in proteins. The following issues were addressed: (1) Whether there is a relation between the score (S(mem)) of a model and its closeness to the "nativelike" conformation? (2) Is it possible to recognize a correct model among misfolded and erroneous ones? (3) To what extent the score of a homology-built model is sensitive to errors in sequence alignment? To answer the first question, two test cases were considered: (i) Several models of bovine aquaporin-1 (target protein) were built on the structural templates provided by its homologs with known X-ray structure. (ii) Side chains in the spatial models of visual rhodopsin and cytochrome c oxidase were rebuilt based on the backbone scaffolds taken from their crystal structures, and the resulting models were iteratively fitted into the full-atom X-ray conformations. It was shown that the higher the S(mem) value of a model is, the lower its root-mean-square deviation is from the "correct" (crystal) structure of a target. Furthermore, the "membrane score" method successfully identifies the rhodopsin crystal structure in an ensemble of "rotamer-type" decoys, thus providing the way to optimize mutual orientations of alpha-helices in models of TM domains. Finally, being applied to a set of homology models of rhodopsin built on its crystal structure with systematically shifted alignment, the approach demonstrates a prominent ability to detect alignment errors. We therefore assume that the "membrane score" method will be helpful in optimization of in silico models of TM domains in proteins, especially those in GPCRs.
ID:2 - (2007). A novel method for packing quality assessment of transmembrane alpha-helical domains in proteins. Biochemistry Mosc. 72 (3), 293–300 [+]
Here we present a novel method for assessment of packing quality for transmembrane (TM) domains of alpha-helical membrane proteins (MPs), based on analysis of available high-resolution experimental structures of MPs. The presented concept of protein-membrane environment classes permits quantitative description of packing characteristics in terms of membrane accessibility and polarity of the nearest protein groups. We demonstrate that the method allows identification of native-like conformations among the large set of theoretical MP models. The developed "membrane scoring function" will be of use for optimization of TM domain packing in theoretical models of MPs, first of all G-protein coupled receptors.
ID:186 - (2007). Complementarity of hydrophobic properties in ATP-protein binding: a new criterion to rank docking solutions. Proteins 66 (2), 388–98 [+]
Анализ экспериментально установленных пространственных структур комплексов АТФ-белок был проведен с целью выявить основные закономерности, определяющие молекулярное узнавание аденин-белок. Было показано что основную роль играют гидрофобные котакты и стэкинг, и разработан эффективный метод учета этих взаимодействий в аденин-специфичной оценочной функции.
ID:123 - (2007). Molecular lipophilicity in protein modeling and drug design. Curr. Med. Chem. 14 (4), 393–415 [+]
Hydrophobic interactions play a key role in the folding and maintenance of the 3-dimensional structure of proteins, as well as in the binding of ligands (e.g. drugs) to protein targets. Therefore, quantitative assessment of spatial hydrophobic (lipophilic) properties of these molecules is indispensable for the development of efficient computational methods in drug design. One possible solution to the problem lies in application of a concept of the 3-dimensional molecular hydrophobicity potential (MHP). The formalism of MHP utilizes a set of atomic physicochemical parameters evaluated from octanol-water partition coefficients (log P) of numerous chemical compounds. It permits detailed assessment of the hydrophobic and/or hydrophilic properties of various parts of molecules and may be useful in analysis of protein-protein and protein-ligand interactions. This review surveys recent applications of MHP-based techniques to a number of biologically relevant tasks. Among them are: (i) Detailed assessment of hydrophobic/hydrophilic organization of proteins; (ii) Application of this data to the modeling of structure, dynamics, and function of globular and membrane proteins, membrane-active peptides, etc. (iii) Employment of the MHP-based criteria in docking simulations for ligands binding to receptors. It is demonstrated that the application of the MHP-based techniques in combination with other molecular modeling tools (e.g. Monte Carlo and molecular dynamics simulations, docking, etc.) permits significant improvement to the standard computational approaches, provides additional important insights into the intimate molecular mechanisms driving protein assembling in water and in biological membranes, and helps in the computer-aided drug discovery process.
ID:185 - (2006). Solution of the Spatial Structure of Dimeric Transmembrane Domains of Proteins by Heteronuclear NMR Spectroscopy and Molecular Modeling. Biophysics 51 (S1), S23–S27 [+]
Membrane proteins play an important role in various biological processes. An approach combining
ID:347
NMR spectroscopy with molecular modeling was used to study the spatial structure and intramolecular dynamics of protein transmembrane domains consisting of two interacting α-helices. The approach was tested with model transmembrane domains and yielded detailed atomic-level data on the protein–protein and protein–lipid interactions. - (2006). alpha-Conotoxin GI benzoylphenylalanine derivatives. (1)H-NMR structures and photoaffinity labeling of the Torpedo californica nicotinic acetylcholine receptor. FEBS J. 273 (7), 1373–88 [+]
ID:189 - (2005). Cancer cell injury by cytotoxins from cobra venom is mediated through lysosomal damage. Biochem. J. 390 (Pt 1), 11–8 [+]
Статья посвящена исследованию механизмов цитотоксического действия цитотоксинов (ЦТ) из яда кобр. В данной работе показано, что ЦТ 1 и 2 из яда кобры Naja oxiana, ЦТ 1 из Naja haje и ЦТ 3 из Naja kaouthia способны накапливаться в лизосомах клеток промиелоцитарной лейкемии человека HL60 и аденокарциномы легкого человека A549. Кинетика и концентрационная зависимость накопления ЦТ в лизосомах согласуется с кинетикой и концентрационной зависимостью гибели клеток, что свидетельствует о том, что лизосомы могут быть одной из мишеней ЦТ, а воздействие на эту мишень заключается в концентрационно-зависимой пермеабилизации мембраны лизосом.
ID:93 - (2005). Role of lipid charge in organization of water/lipid bilayer interface: insights via computer simulations. The journal of physical chemistry. B 109 (31), 15052–9 [+]
Anionic unsaturated lipid bilayers represent suitable model systems that mimic real cell membranes: they are fluid and possess a negative surface charge. Understanding of detailed molecular organization of water-lipid interfaces in such systems may provide an important insight into the mechanisms of proteins' binding to membranes. Molecular dynamics (MD) of full-atom hydrated lipid bilayers is one of the most powerful tools to address this problem in silico. Unfortunately, wide application of computational methods for such systems is limited by serious technical problems. They are mainly related to correct treatment of long-range electrostatic effects. In this study a physically reliable model of an anionic unsaturated bilayer of 1,2-dioleoyl-sn-glycero-3-phosphoserine (DOPS) was elaborated and subjected to long-term MD simulations. Electrostatic interactions were treated with two different algorithms: spherical cutoff function and particle-mesh Ewald summation (PME). To understand the role of lipid charge in the system behavior, similar calculations were also carried out for zwitterionic bilayer composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). It was shown that, for the charged DOPS bilayer, the PME protocol performs much better than the cutoff scheme. In the last case a number of artifacts in the structural organization of the bilayer were observed. All of them were attributed to inadequate treatment of electrostatic interactions of lipid headgroups with counterions. Electrostatic properties, along with structural and dynamic parameters, of both lipid bilayers were investigated. Comparative analysis of the MD data reveals that the water-lipid interface of the DOPC bilayer is looser than that for DOPS. This makes possible deeper penetration of water molecules inside the zwitterionic (DOPC) bilayer, where they strongly interact with carbonyls of lipids. This can lead to thickening of the membrane interface in zwitterionic as compared to negatively charged bilayers.
ID:843 - (2005). Comparative analysis of proapoptotic activity of cytochrome c mutants in living cells. Apoptosis 10 (4), 797–808 [+]
В работе докладывается о разработке метода измерения проапоптотическй активности экзогенного цитохрома с в живых клетках. Метод основан на введении белка в цитоплазму клетки с помощью электропорации и выявлении с помощью флуоресцентной микроскопии признаков развития апоптоза в клетках. С помощью данного метода были измерены относительные про-апоптозные активности лошадиного цитохрома с и четырех мутантных вариантов данного белка. Обнаружено, что аминокислотная замена К72W полностью блокирует про-апоптозную активность цитохрома с, но не влияет на его «дыхательную» функцию. Методом КОМИРСИ была впервые оценена минимальная цитоплазматическая концентрация лошадиного цитохрома с, необходимая для индукции апоптоза в клетках
ID:94WEHI-3b. - (2004). High stability of the hinge region in the membrane-active peptide helix of zervamicin: paramagnetic relaxation enhancement studies. Biochem. Biophys. Res. Commun. 325 (3), 1099–105 [+]
Zervamicin IIB is a 16 amino acid peptaibol that forms voltage dependent ion channels with multilevel conductance states in planar lipid bilayers and vesicular systems. Stability of the hinge region and intermolecular interactions were investigated in the N- and C-terminally spin-labelled peptide analogues. Intermolecular and intramolecular paramagnetic enhancement indicates that zervamicin behaves as a rigid helical rod in methanol solution. There are no high amplitude hinge-bending motions, and the peptaibol is monomeric up to concentration 1.5 mM. Stability of the hinge region illustrates the helix stabilising propensity of the Pro residue in membrane mimic environments and implies absence of significant conformational rearrangement due to voltage peptaibol activation.
ID:425 - (2002). New binding site on common molecular scaffold provides HERG channel specificity of scorpion toxin BeKm-1. J. Biol. Chem. 277 (45), 43104–9 [+]
The scorpion toxin BeKm-1 is unique among a variety of known short scorpion toxins affecting potassium channels in its selective action on ether-a-go-go-related gene (ERG)-type channels. BeKm-1 shares the common molecular scaffold with other short scorpion toxins. The toxin spatial structure resolved by NMR consists of a short alpha-helix and a triple-stranded antiparallel beta-sheet. By toxin mutagenesis study we identified the residues that are important for the binding of BeKm-1 to the human ERG K+ (HERG) channel. The most critical residues (Tyr-11, Lys-18, Arg-20, Lys-23) are located in the alpha-helix and following loop whereas the "traditional" functional site of other short scorpion toxins is formed by residues from the beta-sheet. Thus the unique location of the binding site of BeKm-1 provides its specificity toward the HERG channel.
ID:195 - (1999). A solvent model for simulations of peptides in bilayers. I. Membrane-promoting alpha-helix formation. Biophys. J. 76 (5), 2448–59 [+]
В работе дается описание неявно заданной модели мембраны. Показана эффективность модели в предсказании доли альфа-спиральной конформации для нескольких гомопептидов (поли-Leu, поли-Val, поли-Ile, поли-Gly) методом Монте-Карло.
ID:122 - (1995). Processing of heteronuclear NMR relaxation data with the new software DASHA. Appl. Mag. Reson. 9 (4), 581–588 [+]
The new program DASHA is an efficient implementation of common data processing steps for the protein internal dynamic analysis. The “model-free” parameters and their uncertainties (Lipari G., Szabo A.: J. Am. Chem. Soc.104, 4546–4559 (1982) can be calculated from an arbitrary combination of experimental data sets (i.e. heteronuclear1H−15N or1H−13C relaxation times and NOE values at different spectrometer frequencies). Anisotropy of the molecular rotational diffusion could be also taken into account without introduction of the new adjustable parameters into the spectral density functionJ(ω), provided the structure of the molecule is known. Parameters of chemical (conformational) exchange can be estimated from the CPMG spin-lock frequency dependences (Bloomet al.: J. Chem. Phys.42, 1615–1624 (1965); Orekhovet al.: Eur. J. Biochem.219, 887–896 (1994). The program can be used both in the interactive and batch modes. It has sophisticated PostScript plotting facilities.
ID:1046 - (1985). 1H-NMR study of gramicidin A transmembrane ion channel. Head-to-head right-handed, single-stranded helices. FEBS Lett. 186 (2), 168–174 [+]
The structure of [Val1] gramicidin A incorporated into sodium dodecyl-d25 sulphate micelles has been studied by two-dimensional proton NMR spectroscopy. Analysis of nuclear Overhauser effects, spin-spin couplings and solvent accessibility of NH groups show that the conformation of the Na+ complex of gramicidin A in detergent micelles, which in many ways mimic the phospholipid bilayer of biomembranes, is an N-terminal to N-terminal (head-to-head) dimer
ID:144formed by two right-handed, single-stranded β6.3 helices with 6.3 residues per turn, differing from Urry's structure by handedness of the helices.