ATP-driven Na+ transport and Na(+)-dependent ATP synthesis in Escherichia coli grown at low delta mu H+

Abstract

In inverted subcellular vesicles of Escherichia coli grown at high delta mu H+ (neutral pH, no protonophorous uncoupler), ATP-driven Na+ transport and oxidative phosphorylation are completely inhibited by the protonophore CCCP. If E. coli was grown at low delta mu H+, i.e. at high pH or in the presence of uncoupler, some oxidative phosphorylation was observed in the vesicles even in CCCP-containing medium, and Na+ transport was actually stimulated by CCCP. The CCCP-resistant transport and phosphorylation were absent from the unc mutant lacking F0F1 ATPase. Both processes proved to be sensitive to (i) the Na+/H+ antiporter monensin, (ii) the Na+ uniporter ETH 157, (iii) the F0 inhibitors DCCD and venturicidin, and (iv) the F1 inhibitor aurovertin. The CCCP-resistant oxidative phosphorylation was stimulated by Na+ and arrested by oppositely directed delta pNa. These data are consistent with the assumption that, under appropriate growth conditions, the F0F1-type ATPase of E. coli becomes competent in transporting Na+ ions.