AbstractDuring 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 prot