Electrogenic Na+transport byEnterococcus hiraeNa+-ATPase

Abstract

Energy‐dependent generation of a membrane potential (Δψ) (−45 mV, interior negative) was observed in the F₀F₁, H⁺‐ATPase‐defective mutant of Enterococcus hirae. The generation of Δψ was found at high pH (but not at low pH), for which intracellular Na⁺ was required but not extracellular K⁺. The Δψ‐generating activity was induced in cells cultured in media containing high concentrations of Na⁺, and was not observed in the Na⁺‐ATPase mutants. These results suggest that E. hirae Na⁺‐ATPase is responsible for the electrogenic sodium pump.