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 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-binding sites deep inside the transmembrane part of the protein, the missing electrogenicity in state E1 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 E1 conformation of the Na,K-ATPase.
Apell
Hans-Jürgen
HJ
University of Konstanz, Biology, Universitätsstrasse 10, Konstanz 78457, Germany. h-j.apell@uni-konstanz.de
Diller
Anna
A
D000818:Animals; D001665:Binding Sites; D003593:Cytoplasm / Q000737:chemistry / Q000201:enzymology; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D011188:Potassium / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D011522:Protons; D011817:Rabbits; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry* / Q000378:metabolism*
D011522:Protons; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium