Molecular mechanisms of rotational catalysis in the F₀F₁ ATP synthase

Rotation of the F₀F₁ ATP synthase γ subunit drives each of the three catalytic sites through their reaction pathways. The enzyme completes three cycles and synthesizes or hydrolyzes three ATP for each 360°rotation of the γ subunit. Mutagenesis studies have yielded considerable information on the roles of interactions between the rotor γ subunit and the catalytic β subunits. Amino acid substitutions, such as replacement of the conserved γMet-23 by Lys, cause altered interactions between γ and β subunits that have dramatic effects on the transition state of the steady state ATP synthesis and hydrolysis reactions. The mutations also perturb transmission of specific conformational information between subunits which is important for efficient conversion of energy between rotation and catalysis, and render the coupling between catalysis and transport inefficient. Amino acid replacements in the transport domain also affect the steady state catalytic transition state indicating that rotation is involved in coupling to transport.