1987 Volume 107 Issue 11 Pages 835-848
Adenosinetriphosphate (ATP) synthase (FoF1) is a major energy supplying enzyme of cells utilizing the proton motive force. It consists of a catalytic portion called F1 and a proton channel portion called Fo. In order to elucidate the chemical reaction of FoF1, thermophilic FoF1 (TFoF1) was used, because it is stable and could eb reconstituted without Mg-ATP. In contrast to the previous hypotheses on the ATP synthesis, direct measurement of H+ current through TFoF1 incorporated into a planar lipid bilayer, 3H+/ATP stoichiometry was obtained. The primary structure of TFoF1 was established by sequencing its operon deoxyribonucleic acid and subunit peptides. The stereochemistry of the reaction using [16O, 17O, 15O, 35S] thiophosphate supported the a pathway for associative nucleophilic displacement on a phosphoric ester without pseudorotation. The diastereoisomeric preference of Cd-ATPγS revealed that the true substrate of TFoF1 is Δ, β, γ, bidentate Mg-ATP, like adenylate kinase. The site directed mutagenesis of the residues of F1 homologous to Mg-ATP binding site of adenylate kinase revealed their essential role in the reaction. Mitchell's chemiosmotic theory was refined by these results.
