In vitro protein translocation into inverted membrane vesicles prepared from Vibrio alginolyticus is stimulated by the electrochemical potential of Na+ in the presence of Escherichia coli SecA.

A protein translocation system was reconstituted from inverted membrane vesicles prepared from Na+ pump-possessing Vibrio alginolyticus and purified Escherichia coli SecA. The translocation required ATP and was stimulated by the functioning of the Na+ pump, suggesting that the electrochemical potential of Na+, but not that of H+, is important for protein translocation in Vibrio.