Rubidium Movements in Vesicles Reconstituted with Na,K-ATPase, Measured in the Absence of ATP and Pi, in the Presence of Either Ligand, and in the Presence of Both Ligands: Role of the “Occluded Staté in Allowing for the Control of the Direction of Ion Movements

S. J.D. Karlish, W. D. Stein

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Abstract

This chapter discusses the role of the major nonphosphorylated conformations of the Na/K-pump in the movement of potassium ions and the implications of this role for sodium/potassium pumping. The experiments involve the measurements of ion fluxes into and out of phospholipid vesicles containing the reconstituted Na, K-ATPase from pig kidney. Such vesicles sustain the conventional ATP-dependent Na/K exchanges. A study of the rubidium movements in the presence of ATP or Pi, of both ATP and Pi, and in the absence of ATP and Pi, are used to throw light on the mechanism of the action of the pump and the physiological control of the direction of ion pumping and the associated ATP breakdown. The experimental method used is summarized in the chapter. Physical techniques, in particular fluorescence spectroscopy as well the use of controlled proteolytic digestion, have identified two clearly different conformations of the Na/K pump enzyme, E1 and E2. The salient features of the interconversions between these two forms are summarized in the chapter.

Original languageEnglish
Pages (from-to)425-449
Number of pages25
JournalCurrent Topics in Membranes and Transport
Volume19
Issue numberC
DOIs
StatePublished - 1 Jan 1983

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