The thermal unfolding and domain structure of Na+/K+-exchanging ATPase: A scanning calorimetry study

The thermal unfolding and domain structure of Na+/K+-ATPase from pig kidney were studied by high-sensitivity differential scanning calorimetry (HS-DSC). The excess heat capacity function of Na+/K+-ATPase displays the unfolding of three cooperative domains with midpoint transition temperatures (Td) of 320.6, 327.5, 331.5 K, respectively. The domain with Td=327.5 K was identified as corresponding to the β subunit, while two other domains belong to the α subunit. The thermal unfolding of the low-temperature domain leads to large changes in the amplitude of the short-circuit current, but has no effect on the ATP hydrolysing activity. Furthermore, dithiothreitol or 2-mercaptoethanol treatment causes destruction of this domain, accompanied by significant disruption of the ion transporting function and a 25% loss of ATPase activity. The observed total unfolding enthalpy of the protein is rather low (≈12 J·g-1), suggesting that thermal denaturation of Na+/K+-ATPase does not lead to complete unfolding of the entire molecule. Presumably, transmembrane segments retain most of their secondary structure upon thermal denaturation. The binding of physiological ligands results in a pronounced increase in the conformational stability of both enzyme subunits.

Grinberg AV, Gevondyan NM, Grinberg NV, Grinberg VY

IBCH: 1782
Ссылка на статью в журнале: http://doi.wiley.com/10.1046/j.0014-2956.2001.02436.x
Кол-во цитирований на 12.2023: 33
Информация пока не проверена модераторами