The dicyclohexylcarbodiimide-binding protein c of ATP synthase from Escherichia coli is not sufficient to express an efficient H+ conduction.

Bacteriophage Mu was inserted into the unc genes of Escherichia coli. The resulting mutation AS12 had a polar effect on the unc operon: membranes of the mutant AS12 contained the dicyclohexylcarbodiimide-binding protein c and the protein a as sole subunits of the ATP synthase. It was shown by peptide mapping and amino acid analysis of the fragments that protein c from mutant AS12 was identical with the wild-type protein c. The absence of subunit b in mutant AS12 drastically lowered the H+ conduction dependent on the membrane-integrated moiety (F0) of the ATP synthase. This suggests that both subunits b and c are necessary for an efficient expression of H+ conduction.