[Regulation of Na+-K+-ATPase: effect of Mg and Ca ions]

Abstract

The participation of Mg2+ and Ca2+ in complicated mechanisms of Na+, K(+)-ATPase regulation is discussed in the survey. The regulatory actions of Mg2+ on Na+, K(+)-ATPase such as its participation in phosphorylation and dephosphorylation of the enzyme, ADP/ATP-exchange inhibition, cardiac glycosides and vanadate binding with the enzyme, conformational changes induction during ATPase cycle are reviewed in detail. Some current views of mechanisms of above mentioned Mg2+ regulatory effects are discussed. The experimental evidence of Ca2+ immediate influence on the functional activity of Na+, K(+)-ATPase (catalytic, transport and glycoside-binding) are given. It's noted that these effects are based on the conformational changes in the enzyme and also on the phase transition in membrane induced by Ca2+. Unimmediate action of Ca2+ on Na+, K(+)-ATPase is also discussed, especially due to its effect on other membrane systems functionally linked with Na(+)-pump (for instance, due to Na+/Ca(+)-exchanger activation). It's concluded that Mg2+ and Ca2+ as "universal regulators" of the cell effectively influence the functional activity and conformational states of Na+, K(+)-ATPase.