title: Cation exchanges of yeast in the absence of magnesium.
abstract: Environmental Mg2+ was found to influence the K+/Na+ exchange rate of metabolizing yeast. Addition of EDTA increased the exchange rate and Mg2+ reversed the effect of EDTA. Yeast starved in the absence of Mg2+ exchanged cellular K+ or Na+ for external H+ when maintained at acidic pH. The exchange rate depended on cellular pH and showed the same kinetics for both K+ and Na+. At acidic pH, the presence of external cations neither inhibited H+ absorption nor changed the cation/H+ 1 : 1 stoichiometry. At neutral pH, external cations inhibited H+ influx but did not change the cation efflux. The K+/Na+ exchange is discussed as electrically coupled and the K+/H+ and Na+/H+ exchanges as electroneutral antiports.
mesh_terms: D001693:Biological Transport, Active / Q000187:drug effects; D004492:Edetic Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
chemical_list: D004492:Edetic Acid; D012964:Sodium; D008274:Magnesium; D011188:Potassium