A respiratory-driven and an artificially driven ATP synthesis in mutants of Vibrio parahaemolyticus lacking H+-translocating ATPase

Mutants of Vibrio parahaemolyticus lacking the H+-translocating ATPase were isolated to evaluate both the role of this enzyme and the possibility of the involvement of other cation-translocating ATPase in the energy transduction in this organism. Dicyclohexylcarbodiimide-sensitive ATPase activity which represents the H+-translocating ATPase was not detected either in the membrane vesicles or in the cytosol of the mutants. Three major subunits, alpha, beta and gamma, of the H+-translocating ATPase were missing in the membranes of the mutants. Although ATP was synthesized in wild type cells when an artificial H+ gradient was imposed, little ATP was synthesized in the mutants. However, we observed a large ATP synthesis driven by the respiration not only in the wild type but also in the mutants. The respiratory-driven ATP synthesis in wild type was inhibited by an H+ conductor, carbonylcyanide m-chlorophenylhydrazone, by about 50%. On the other hand, the ATP synthesis in the mutants was not affected by the H+ conductor. Since this organism possesses a respiratory Na+ pump, Na+-coupled ATP synthesis might take place. In fact, we observed some ATP synthesis driven by an artificially imposed Na+ gradient both in the wild type and the mutant.