ANTIBODIES AGAINST SUBUNITS OF F-0 SECTOR OF ATP SYNTHASE FROM SACCHAROMYCES-CEREVISIAE - STIMULATION OF ATP SYNTHASE BY SUBUNIT-8-REACTIVEANTIBODIES AND INHIBITION BY SUBUNIT-9-REACTIVE ANTIBODIES

Polyclonal antibodies against the three purified proteolipids of the F -0 sector [subunit 6 (Su6), subunit 8 (Su8), subunit 9 (Su9)] and agai nst the beta subunit (F-1) 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 migr ating with the same molecular mass as that of the purified protein. Mi tochondria were incubated with Ige of each antiserum and oxidative pho sphorylation was measured. Anti-Su6 IgC, as anti-su beta IgG, was with out effect whereas anti-Su9 IgG decreased both respiration and ATP-syn thesis 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 IG i nhibited ATP hydrolysis whereas anti-Su8 IgG stimulated this activity. Antimycin titration of phosphorylation and respiration rates demonstr ated that anti-Su9 IgG decreased the H+/ATP ratio and promoted a H+ le ak, whereas anti-Su8 IgG increased H+/ATP without modification of the proton permeability. Anti-Su9 IgG decreased proton-motive force wherea s anti-Su8 IgG did not. It is proposed that both antibodies promoted o pposite mechanistic changes of the H+/ATP stoichiometry of the ATP syn thase, and that in vivo Su8 could have a negative regulatory role in t he oxidative phosphorylation process.