Energy-dependent transformation of the catalytic activities of the mitochondrial F-0 center dot F-1-ATP synthase

The ADP(Mg2+)-deactivated, azide-trapped F-0.F(1)ATPase of coupled submitoc hondrial particles is capable of ATP synthesis being incapable of ATP hydro lysis and ATP-dependent Delta<(mu)over bar>(H) + generation [FEBS Lett. (19 95) 366, 29-32]. This puzzling phenomenon was studied further. No ATPase ac tivity of the submitochondrial particles catalyzing succinate-supported oxi dative phosphorylation in the presence of azide was observed when ATP was a dded to the assay mixture after an uncoupler. Rapid ATP hydrolysis was dete cted in the same system when ATP followed by an uncoupler was added. Less t han 5% of the original ATPase activity was seen when the reaction (assayed with ATP-regenerating system) was initiated by the addition of ATP to the a zide-trapped coupled particles oxidizing succinate either in the presence o r in the absence of the uncoupler. High ATP hydrolytic activity was reveale d when the reaction was started by the simultaneous addition of the ATP plu s uncoupler to the particles generating Delta<(mu)over bar>(H) +. The energ y-dependent conversion of the enzyme into latent uncoupler-activated ATPase was prevented by free ADP (K-i approximate to 20 mu M) and was greatly enh anced after multiple turnovers in oxidative phosphorylation. The results su ggest that the catalytic properties of F-0.F-1 are Delta<(mu)over bar>(H) dependent which is in accord with our hypothesis on different conformation al states of the enzyme participating in ATP synthesis or hydrolysis. (C) 1 999 Federation of European Biochemical Societies.