Purification and Characterization of a Glycerol-Resistant CF(0)-CF(1) and CF(1)-ATPase from the Halotolerant Alga Dunaliella bardawil

The isolation of the chloroplast ATP synthase complex (CF₀-CF₁) and of CF₁ from Dunaliella bardawil is described. The subunit structure of the D. bardawil ATPase differs from that of the spinach in that the D. bardawil α subunit migrates ahead of the β subunit and ε-migrates ahead of subunit II of CF₀ when separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The CF₁ isolated from D. bardawil resembles the CF₁ isolated from Chladmydomonas reinhardi in that a reversible, Mg²⁺-dependent ATPase is induced by selected organic solvents. Glycerol stimulates cyclic photophosphorylation catalyzed by D. bardawil thylakoid membranes but inhibits photophosphorylation catalyzed by spinach thylakoid membranes. Glycerol (20%) also stimulates the rate of ATP-P_i exchange catalyzed by D. bardawil CF₀-CF₁ proteoliposomes but inhibits the activity with the spinach enzyme. The ethanol-activated, Mg²⁺-ATPase of the D. bardawil CF₁ is more resistant to glycerol inhibition than the octylglucoside-activated, Mg²⁺-ATPase of spinach CF₁ or the ethanol-activated, Mg²⁺-dependent ATPase of the C. reinhardi CF₁. Both cyclic photophosphorylation and ATP-P_i exchange catalyzed by D. bardawil CF₀-CF₁ are more sensitive to high concentrations of NaCl than is the spinach complex.