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Evidence for a selective and electroneutral K + /H + ‐exchange in Saccharomyces cerevisiae using plasma membrane vesicles
Author(s) -
Camarasa Carole,
Prieto Susana,
Ros Roc,
Salmon JeanMichel,
Barre Pierre
Publication year - 1996
Publication title -
yeast
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.923
H-Index - 102
eISSN - 1097-0061
pISSN - 0749-503X
DOI - 10.1002/(sici)1097-0061(199610)12:13<1301::aid-yea18>3.0.co;2-a
Subject(s) - vesicle , membrane , saccharomyces cerevisiae , electrochemical gradient , biophysics , membrane transport , chromatography , membrane potential , quenching (fluorescence) , mediated transport , efflux , biology , atpase , biochemistry , fluorescence , chemistry , yeast , enzyme , physics , quantum mechanics
The existence of a K + /H + transport system in plasma membrane vesicles from Saccharomyces cerevisiae is demonstrated using fluorimetric monitoring of proton fluxes across vesicles (ACMA fluorescence quenching). Plasma membrane vesicles used for this study were obtained by a purification/reconstitution protocol based on differential and discontinuous sucrose gradient centrifugations followed by an octylglucoside dilution/gel filtration procedure. This method produces a high percentage of tightly‐sealed inside‐out plasma membrane vesicles. In these vesicles, the K + /H + transport system, which is able to catalyse both K + influx and efflux, is mainly driven by the K + transmembrane gradient and can function even if the plasma membrane H + ‐ATPase is not active. Using the anionic oxonol VI and the cationic DISC 2 (5) probes, it was shown that a membrane potential is not created during K + fluxes. Such a dye response argues for the presence of a K + /H + exchange system in S. cerevisiae plasma membrane and established the non‐electrogenic character of the transport. The maximal rate of exchange is obtained at pH 6·8. This reversible transport system presents a high selectivity for K + among other monovalent cations and a higher affinity for the K + influx into the vesicles (exit from cells). The possible role of this K + /H + exchange system in regulation of internal potassium concentration in S. cerevisiae is discussed.