Do H+ ions obscure electrogenic Na+ and K+ binding in the E1 state of the Na,K-ATPase?

In contrast to other P-type ATPases, the Na,K-ATPase binding and release of ions on the cytoplasmic side, to the state called E-1, is not electrogenic with the exception of the third Na+. Since the high-resolution structure of the closely related SR Ca-ATPase in state E-1 revealed the ion-binding sites deep inside the transmembrane part of the protein, the missing electrogenicity in state E-1 can be explained by an obscuring counter-movement of H+ ions. Evidence for such a mechanism is presented by analysis of pH effects on Na+ and K+ binding and by electrogenic H+ movements in the E-1 conformation of the Na,K-ATPase. (C) 2002 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.