A thorough analysis of proteins capable of interacting with presynaptic receptors of α-latrotoxin was carried out. The protein components of receptor complexes were purified from rat brain membranes by the affinity chromatography on immobilized α-latrotoxin and antibodies to the cytoplasmic moiety of the calciumindependent receptor of α-latrotoxin (CIRL) and analyzed then by mass spectrometry. Several proteins were identified, with structural proteins, intracellular signal proteins, and proteins involved in the endocytosis and transport of synaptic vesicles being among them. © 2008 MAIK Nauka.