Altered stoichiometry of the Na,K-ATPase.
With inside-out membrane vesicles derived from human red cells and incubated at pH > or = 6.6, an altered sodium pump stoichiometry (1Na+:2K+) associated with altered charge transfer is observed when the cytoplasmic Na+ concentration is reduced to very low levels (0.2 mM). With increased proton concentration (approximately pH 6.0), protons can substitute for Na+ or K+ ions such that the Na,K-ATPase can effect either electroneutral Na+/H+ exchange (K+ absent), H+/K+ exchange (Na+ absent), or H(+)-plus-Na+ cotransport in exchange for K+ (low Na+ concentration). Evidence that the stoichiometries of these exchanges are 3Na+/3H+, 2H+/2K+ and 1H(+)-plus-1Na+/2K+, respectively, is presented.
Blostein
R
R
Montreal General Hospital Research Institute, Quebec, Canada.
Polvani
C
C
D004912:Erythrocytes / Q000201:enzymology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D011188:Potassium / Q000097:blood; D012964:Sodium / Q000097:blood; D000254:Sodium-Potassium-Exchanging ATPase / Q000097:blood / Q000737:chemistry / Q000378:metabolism*
D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium