ATP-dependent rotation of mutant ATP synthases defective in proton transport

During ATP hydrolysis, the gamma epsilon c(10) complex (gamma and epsilon subunits and a c subunit ring formed from 10 monomers) of F0F1 ATPase ( ATP synthase) rotates relative to the alpha(3)beta(3)delta ab(2) complex, leading to proton transport through the interface between the a subunit and the c subunit ring. In this study, we replaced the two pertinent residues for proton transport, cAsp-61 and aArg-210 of the c and a subunits, respectively. The mutant enzymes exhibited lower ATPase activities than that of the wild type but exhibited ATP-dependent rotation in planar membranes, in which their original assemblies are maintained. The mutant enzymes were defective in proton transport, as shown previously. These results suggest that proton transport can be separated from rotation in ATP hydrolysis, although rotation ensures continuous proton transport by bringing the cAsp-61 and aArg-210 residues into the correct interacting positions.