Reconstitution of photosynthetic energy conservation. I. Proton movements in liposomes containing reaction center of photosystem I from spinach chloroplasts.

A preparation of reaction centers of photosystem I from spinach chloroplasts was incorporated into lipid vesicles by sonication. Incorporation was tested by chromatography on Sepharose-4B, by comparison of the elution profiles of photosystem-I reaction center liposomes and of free reaction centers. In the presence of reduced N-methylphenazonium methosulfate the reaction center liposomes catalyzed net proton extrusion in the light, but at the same time showed light-induced quenching of 9-aminoacridine fluorescence, with similar extent and kinetics as known for chloroplasts. We conclude that we are dealing with two vesicle populations, one right side-out and one inside-out with respect to the orientation of the incorporated reaction center complex. Net proton movements are influenced by the nature of the cations present in the suspending medium, and the possibilities for effects of surface charge on these movements are discussed.