Proton/sodium ion antiport in Escherichia coli

Abstract

In anaerobic suspensions of Escherichia coli, after H+ ions have been translocated outwards across the plasma membrane by a respiratory pulse, re-equilibration is catalysed by Na+. The sudden addition of a Na+ salt causes the effective outward translocation of H+ by an electroneutral process. We conclude that the plasma membrane of E. coli contains a Na+/H+ antiport system that normally translocates Na+ outwards under the influence of an inwardly directed H+-activity gradient.