Volume 2, Number 1/2, p. 19-24
G. Chkadua, E. Nozadze, M. Leladze and Z. Kometiani
I. Beritashvili Institute of Physiology, Georgian Academy of Sciences, 14 Gotua St, 380060 Tbilisi, Georgia
Activation mechanism for the Na,K-ATPase system in an excess of Mg2+
It is known that there exist Mg2+ (OPM), MgATP (SPO) and ATPfree (OPA) dependent Na,K-ATPase cycles, which are characterized by deposphorylation of the Mg2+, MgATP and ATPfree bound phosphorylated intermediate. The study of the OPM régime has demonstrated that an increase in the K+ concentration results in changing the number of Na+-sites of essential activators from 3 to 4. The study of the Na+ activated Na,K-ATPase mechanism in the SPO and OPA régimes at high concentrations of K+ (>125 mM) made it evident that the number of Na+-sites equals 3. K+ is not an essential activator and the variation of the number of its sites (0, 1 or 2) in the OPM régime is not Na+ concentration-dependent, while in the SPO régime the number of K+ sites equals 2. Relying on this evidence and using the principle of a minimal model, a kinetic scheme of the OPM régime has been created.
Keywords: essential activators, ion sites, modifiers with a partial effect, Na,K-ATPase.