title: ATP-driven exchange of Na+ and K+ ions by Streptococcus faecalis.
abstract: We describe the characterization of KtrII, a novel potassium transport system of Streptococcus faecalis, first discovered by H. Kobayashi [1982) J. Bacteriol. 150, 506-511). KtrII requires sodium ions and mediates the stoichiometric exchange of internal Na+ for external K+. Potassium accumulation is not energized by the electrochemical potentials of either H+ or Na+; the energy source is probably ATP. Two lines of evidence indicate that KtrII is a manifestation of the sodium-stimulated ATPase reported earlier (Heefner, D. L., and Harold, F. M. (1982) Proc. Natl. Acad. Sci. U.S.A. 79, 2798-2802). (i) Mutants that lack the ATPase also lack KtrII, and revertants recover both in parallel. (ii) KtrII and the Na+-ATPase are induced in parallel when cells are grown on media rich in sodium, particularly under conditions that limit the generation of a proton potential. KtrII is not induced in response to K+ deprivation. We propose that the Na+-ATPase exchanges Na+ for K+ ions.
authors.forename: Y
authors.initials: Y
authors.lastname: Kakinuma
authors.forename: F M
authors.initials: FM
authors.lastname: Harold
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D001693:Biological Transport, Active; D027682:Cation Transport Proteins; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D004563:Electrochemistry; D013293:Enterococcus faecalis / Q000378:metabolism*; D009154:Mutation; D011188:Potassium / Q000378:metabolism*; D006180:Proton-Translocating ATPases; D012964:Sodium / Q000378:metabolism*
chemical_list: D027682:Cation Transport Proteins; D004024:Dicyclohexylcarbodiimide; D000255:Adenosine Triphosphate; D012964:Sodium; D000251:Adenosine Triphosphatases; C021838:sodium-translocating ATPase; D006180:Proton-Translocating ATPases; D011188:Potassium