Isolation of alpha-subunits of factor F1 from submitochondrial particles and the reconstitution of active ATPase from isolated alpha-subunits and beta-subunits bound to the mitochondrial membrane

The alpha-subunits of factor-F1 ATPase are removed by extraction of submitochondrial particles with 1.75 M-LiCl, with the consequent loss of ATPase activity. ATPase activity is reconstituted by incubation of LiCl-extracted particles with purified alpha-subunits, and the reconstituted ATPase activity is oligomycin-sensitive. Reconstitution is enhanced by maintenance of the alpha-subunits in reduced form by dithiothreitol or NaBH4 and by modification of the alpha-subunits by p-chloromercuribenzoate, iodoacetic acid or N-ethylmaleimide. Experiments with the mixed anhydride of ATP and mesitylene-carboxylic acid, which was previously shown to interact with the F1 active site, localized on the beta-subunits, indicate that the active site of ATPase is shielded by the alpha-subunits.