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Commercial ATP containing traces of vanadate alters the response of (Na+ + K+)ATPase to external potassium

Nature volume 272, pages 551552 (06 April 1978) | Download Citation

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Abstract

WE have reported that the puzzling inhibition of (Na+ + K+)ATPase preparations by K+ ions, at concentrations insufficient to displace Na+ ions from the intracellular Na+-loading sites, was observed only when Sigma ‘Sigma-grade’ ATP was used as a substrate1. The effect was attributed to a contaminant of the ATP, which bound to the enzyme reversibly but with a high affinity; and because ‘Sigma-grade’ ATP is unique in being prepared from muscle, we suggested that the inhibitor might have a physiological role. Similar conclusions were reached independently by Cantley and Josephson2,3, and they and their colleagues have now identified the contaminant as ortho-vanadate4. The inhibition of (Na+ + K+)ATPase by vanadate plus K+ ions is of interest both for its possible physiological significance—traces of vanadate occur widely in animal tissues5—and for its possible use in elucidating the mechanism of the sodium pump. From both points of view it is desirable to know whether the K+ ions act at the intracellular or extracellular surface of the membrane, and we report here experiments on resealed red cell ghosts showing that the action of K+ ions is at the extracellular surface. In the following paper, Cantley et al.6 describe experiments with intact red cells suggesting that the vanadate ions act at the intracellular surface.

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Affiliations

  1. Department of Biophysics, University of Maryland School of Medicine, Baltimore, Maryland 21201

    • L. A. BEAUGÉ
  2. Physiological Laboratory, University of Cambridge, Cambridge, UK

    • I. M. GLYNN

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https://doi.org/10.1038/272551a0

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