ATP-DRIVEN NA+ TRANSPORT AND NA+-DEPENDENT ATP SYNTHESIS IN ESCHERICHIA-COLI GROWN AT LOW DELTA(MU)OVER-BAR(H)+

In inverted subcellular vesicles of Escherichia coli grown at high DELTAmu(H)+BAR (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 DELTAmu(H)+BAR, 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 DELTApNa. 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.