Antibodies against subunits of F0 sector of ATP synthase from Saccharomyces cerevisiae. Stimulation of ATP synthase by subunit-8-reactive antibodies and inhibition by subunit-9-reactive antibodies.

Polyclonal antibodies against the three purified proteolipids of the F0 sector [subunit 6 (Su6), subunit 8 (Su8), subunit 9 (Su9)] and against the beta subunit (F1) of ATP synthase were raised in rabbits. All antisera showed ELISA reactivities with F0F1-ATPase. Antisera used to immunoblot partially purified ATP synthase labeled a single band migrating with the same molecular mass as that of the purified protein. Mitochondria were incubated with IgG of each antiserum and oxidative phosphorylation was measured. Anti-Su6 IgG, as anti-Su beta IgG, was without effect whereas anti-Su9 IgG decrease both respiration and ATP-synthesis rates, resulting in a decrease of ATP/O. In contrast, anti-Su8 IgG enhanced respiratory control and stimulated the ATP-synthesis rate, resulting in an increase of ATP/O. In the same manner, anti-Su9 IgG inhibited ATP hydrolysis whereas anti-Su8 IgG stimulated this activity. Antimycin titration of phosphorylation and respiration rates demonstrated that anti-Su9 IgG decreased the H+/ATP ratio and promoted a H+ leak, whereas anti-Su8 IgG increased H+/ATP without modification of the proton permeability. Anti-Su9 IgG decreased proton-motive force whereas anti-Su8 IgG did not. It is proposed that both antibodies promoted opposite mechanistic changes of the H+/ATP stoichiometry of the ATP synthase, and that in vivo Su8 could have a negative regulatory role in the oxidative phosphorylation process.