Regulation of potassium fluxes in Saccharomyces cerevisiae.
To investigate the regulation of K+ fluxes in Saccharomyces cerevisiae the dependence of K+ efflux and Rb+ influx on [K+]i, pHi, [Na+]i, membrane potential, cell volume, and turgor pressure were studied in cells with different K+ contents. By decreasing the cell volume with osmotic shocks and the cellular pH with butyric acid the following was found. (1) The K+ efflux induced by uncouplers decreases simultaneously with the decrease of the K+ content of the cell, but the process was insensitive to [K+]i, pHi, cell volume and turgor pressure. The internal presence of Na+ inhibited this K+ efflux. (2) The increase of the Vmax of Rb+ influx observed in low-K+ cells is due to the decrease of the pHi and probably mediated by the increase of the activity of the plasma membrane ATPase. The Vmax is independent of [K+]i, [Na+]i, cell volume and turgor pressure. (3) The decrease in the Km of Bt+ influx observed in low-K+ cells does not depend directly on [K+]i, pHi, cell volume or turgor pressure. If Na+ is present, [Na+]i might be directly involved in the regulation of the Km.
Ramos
J
J
Departamento de Microbiología, Escuela Técnica Superior de Ingenieros Agrónomos, Córdoba, Spain.
Haro
R
R
Rodríguez-Navarro
A
A
D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D009154:Mutation; D011188:Potassium / Q000378:metabolism*; D012413:Rubidium / Q000493:pharmacokinetics; D012441:Saccharomyces cerevisiae / Q000378:metabolism*
D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D012413:Rubidium; D011188:Potassium