Do Hþ ions obscure electrogenic Naþ and Kþ binding in the E1 state of the Na,K-ATPase?

Abstract In contrast to other P-type ATPases, the Na,K-ATPase binding and release of ions on the cytoplasmic side, to the state called E1, is not electrogenic with the exception of the third Na+. Since the high-resolution structure of the closely related SR Ca-ATPase in state E1 revealed the ion-bind-ing sites deep inside the transmembrane part of the protein, the missing electrogenicity in state E1 can be explained by an ob-scuring counter-movement of H+ ions. Evidence for such a mechanism is presented by analysis of pH e¡ects on Na+ and K+ binding and by electrogenic H+ movements in the E1 con-formation of the Na,K-ATPase