Electrogenic binding of ions at the cytoplasmic side of the Na+,K+-ATPase | Sciact

Electrogenic binding of ions at the cytoplasmic side of the Na+,K+-ATPase Научная публикация

Журнал

Biochemistry (Moscow), Supplement Series A: Membrane and Cell Biology
ISSN: 1990-7478 , E-ISSN: 1990-7494

Вых. Данные

Год: 2015, Том: 9, Номер: 2, Страницы: 92-99 Страниц : 8 DOI: 10.1134/s1990747815020105

Авторы

Tashkin V.Yu. ¹ , Gavrilchik A.N. ¹ , Ilovaisky A.I. ² , Apell H.-J. ³ , Sokolov V.S. ¹

Организации

1	Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninskii pr., 31, build. 4, Moscow, 119071, Russia
2	Zelinsky Institute of Organic Chemistry, Russian Academy of Science, Moscow, Leninskii pr., 47, Moscow, 119991, Russia
3	Department of Biology, University of Konstanz, Fach 635, Konstanz, 78457, Germany

Electrogenic binding of ions from the cytoplasmic side of the Na+,K+-ATPase has been studied by measurements of changes of the membrane capacitance and conductance triggered by a jump of pH or of the sodium-ion concentration in the absence of ATP. The pH jumps were performed in experiments with membrane fragments containing purified Na+,K+-ATPase adsorbed to a bilayer lipid membrane (BLM). Protons were released in a sub-millisecond time range from a photosensitive compound (caged H+) triggered by a UV light flash. The sodium concentration jumps were carried out by a fast solution exchange in experiments with membrane fragments attached to a solid-supported membrane deposited on a gold electrode. The change of the membrane capacitance triggered by the pH jump depended on the sodium-ion concentration. Potassium ions had a similar effect on the capacitance change triggered by a pH jump. The effects of these ions are explained by the their competition with protons in the binding sites on cytoplasmic side of the Na+,K+-ATPase. The approximation of the experimental data by a theoretical model yields the dissociation constants, K, and the cooperativity coefficients, n, of the binding sites for sodium ions (K = 2.7 mM, n = 2) and potassium ions (K = 1.7 mM, n = 2). In the presence of magnesium ions the apparent dissociation constants of sodium increased. A possible reason of the inhibition of sodium-ion binding by magnesium ions can be an electrostatic or conformational effect of magnesium ions bound to a separate site of the Na+,K+-ATPase close to the entrance to the sodium-ion binding sites.

Tashkin V.Y. , Gavrilchik A.N. , Ilovaisky A.I. , Apell H.-J. , Sokolov V.S.
Electrogenic binding of ions at the cytoplasmic side of the Na+,K+-ATPase
Biochemistry (Moscow), Supplement Series A: Membrane and Cell Biology. 2015. V.9. N2. P.92-99. DOI: 10.1134/s1990747815020105 WOS Scopus OpenAlex

Web of science:	WOS:000359930100004
Scopus:	2-s2.0-84931266377
OpenAlex:	W2121641113

БД	Цитирований
OpenAlex	2
Scopus	4
Web of science	3