Effect of dimethylsulfoxide on ATP synthesis by mitochondrial soluble F1-ATPase

F1-ATPase isolated from bovine heart mitochondria catalyzes the synthesis of enzyme-bound ATP from externally added ADP and Pi in the presence of dimethylsulfoxide (DMSO) (Sakamoto, J. & Tonomura, Y. (1983) J. Biochem. 93, 1601-1614). When the concentration of DMSO in the reaction medium was decreased from 40% to 10% (w/v), the maximal amount of ATP formed decreased from 0.50 to 0.14 mol/mol F1 and the Pi concentration required for the half-maximal amount of ATP formed increased from 0.7 to 11 mM. On the other hand, the ADP concentration required for the half-maximal value and the rate of ATP formation were unaffected by the decrease in the DMSO concentration. These results suggest that DMSO increases the affinity of F1 and Pi and shifts the equilibrium from the enzyme-ADP-Pi complex to the enzyme-ATP complex during the ATP synthesis.