Coupling between H+ entry and ATP formation in Escherichia coli

ATP synthesis driven by a pH gradient was studied in wild type Escherichia coli and in a mutant lacking functional membrane bound Ca++, Mg++-stimulated adenosine 5′-triphosphatase (BF₀F₁; EC 3.6.1.3). In the wild type, ATP synthesis required the presence of mobile ions other than H+; ATP synthesis was not observed in the mutant. Direct measurement of internal pH also showed that when ATP synthesis occurred in the wild type, acidification of the cell was more rapid than in the mutant. These observations provide direct evidence in support of the idea that BF₀F₁ catalyzes an obligatory coupling between H+ entry and ATP synthesis.