Reconstitution of Purple Membrane Vesicles Catalyzing Light-driven Proton Uptake and Adenosine Triphosphate Formation

Abstract The purple membrane from Halobacterium halobium was incorporated into phospholipid vesicles. On illumination (2 x 106 ergs per cm2 per s) the reconstituted vesicles took up protons (50 to 200 ng of ions H+ per mg of purple protein) which were released in the dark. Addition of valinomycin accelerated both the rate of uptake in the light and the release of protons in the dark. Uncouplers of oxidative phosphorylation abolished the uptake of protons. Inclusion of the mitochondrial oligomycin-sensitive ATPase during reconstitution yielded vesicles which catalyzed light-dependent phosphorylation. These reconstituted vesicles represent a simple model system for a biological proton pump capable of generating ATP from ADP and Pi.