| Abstract: | During the last years we have examined structure—function relationships in the Na+/K+-ATPase with respect to interactions of the external cations with the pump molecule. We have analysed in voltage-clamp experiments the influence of extracellular Na+and K+on the current generated by Na+/K+-pumps expressed inXenopusoocytes. Our results demonstrated that external Na+and K+have to pass an access channel in the electrical field of the membrane to reach their binding sites. This external access, therefore, is voltage-dependent and is affected by lysine residues within the cytoplasmic N-terminus, by glutamic acid residues in intramembraneous domains, the ouabain sensitivity and phosphorylation by protein kinases. |
