Properties of Membrane Fractions Prepared by Chromatophore-Liposome Fusion

Intracytoplasmic membrane vesicles (chromatophores) isolated from Rhodopseudomonas capsulata cells were fused with liposomes by a pH transition procedure. Vesicles o f lower density and higher lipid contents and larger diameter than chromatophores were obtained. Similar results were observed by Ca2+ induced fusion and by the freeze-thawing method. Respiratory and light-induced electron transport were measured in chromatophores and fused vesicles. Light-induced reaction center bleaching was observed in all types o f vesicles, whereas repiratory electron transport was substantially diminished by lipid incorporation. Ubiquinone 10 restored to some extent respiratory electron transport and oxidative phosphorylation and it m odified the photophosphorylation kinetics under continuous light. Electrochromic carotenoid band-shift and the 9-aminoacridine fluorescence quenching indicate that the capacity o f the fused vesicles to maintain an electrochemical proton gradient has not been substantially diminished. From the kinetics of 9-aminoacridine quenching an increased K+-permeability seems to be apparent.