Catalytic sites of Escherichia coli F1-ATPase.

The catalytic site of Escherichia coli F1-ATPase is reviewed in terms of structure and function. Structural prediction, biochemical analyses, and mutagenesis experiments suggest that the catalytic site is formed primarily by residues 137-335 of beta-subunit. Subdomains of the site involved in phosphate-bond cleavage/synthesis and adenine-ring binding are discussed. Ambiguities inherent in steady-state catalytic measurements due to catalytic site cooperativity are discussed, and the advantages of pre-steady-state ("unisite") techniques are emphasized. The emergence of a single high-affinity catalytic site occurs as a result of F1-oligomer assembly. Measurements of unisite catalysis rate and equilibrium constants, and their modulation by varied pH, dimethylsulfoxide, and mutations, are described and conclusions regarding the nature of the high-affinity catalytic site and mechanism of catalysis are presented.