Does F1-ATPase subunit γ turn in the wrong direction?

Analyzing the direction of F-1-ATPase subunit gamma rotation, its shape and non-random distribution of surface residues, a mechanism is proposed for how gamma induces the closing/opening of the catalytic sites at beta/alpha interfaces: by keeping contact with the mobile domain of subunits beta at the 'jaw' (D386, the seven consecutive hydrophobic residues and D394/E395), rotating gamma works as a screw conveyer within the barrel of (alpha,beta)(3). Mutations of the conveyer contacts are predicted to inhibit. Rotating wheel cartoons illustrate enzyme turnover and conformational changes. Steric clashes, polar interactions and also substrate limitations lead to specific stops. Because it is constructed as a stepper, gamma prevents uncoupling at high energy charge. (C) 2002 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.