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Cell Biology International (1996) 20, 67–72 (Printed in Great Britain)

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STRUCTURE–FUNCTION RELATIONSHIPS OF NA+/K+-PUMPS EXPRESSED INXENOPUSOOCYTES

WOLFGANG SCHWARZ and LARISA A. VASILETS*

Max-Planck-Institut für Biophysik, D-60596 Frankfurt/M, Germany

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.

Key words: sodium pump, current–voltage dependence, cation binding mutation, regulation.

^f1Permanent address: Institute of Chemical Physics in Chernogolovka, Russian Academy of Sciences, Chernogolovka, Moscow region 142432, Russia