Some properties of membrane‐bound, solubilized and reconstituted into liposomes H+‐ATPase of vacuoles of Saccharomyces carlsbergensis

Vacuoles of yeast grown in peptone medium possessed high ATPase activity (up to 1 mumol X mg protein-1 X min-1). Membrane-bound and solubilized ATPase activities were insensitive to vanadate and azide, but were inhibited by NO-3 . K+ and cyclic AMP stimulated both membrane-bound and solubilized ATPase activities. Dio-9 activated the membrane form of vacuolar ATPase 1.5-2-fold and did not affect the solubilized enzyme. Solubilized and partially purified vacuolar ATPase was reconstituted with soy-bean phospholipids by a freeze-thaw procedure. ATPase activities in native vacuoles and proteoliposomes were stimulated effectively by Dio-9, the protonophore FCCP and ionophores valinomycin and nigericin. ATP-dependent H+ transport into proteoliposomes was also shown by quenching of ACMA fluorescence. Vacuolar and partially purified ATPase preparations possessed also GTPase activity. Unlike ATPase, however, GTPase was not incorporated as a proton pump into liposomes.