Electrogenic Na+ transport by Enterococcus hirae Na(+)-ATPase.

Energy-dependent generation of a membrane potential (delta psi) (-45 mV, interior negative) was observed in the F0F1, H(+)-ATPase-defective mutant of Enterococcus hirae. The generation of delta psi was found at high pH (but not at low pH), for which intracellular Na+ was required but not extracellular K+. The delta psi-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.