Photooxidase System of Rhodospirillum rubrum 111. The Role of Rhodoquinone and Ubiquinone in the Activity of Preparations of Chromatophores and Photoreaction Centers

Abstract
The role of rhodoquinone and ubiquinone in the O2 photoreducing (photooxidase) activity of R. rubrum was investigated. The sole addition of purified rhodoquinone restored photooxidase activity in isolated chromatophores which were extracted with organic solvents and which were apparently free of secondary acceptor ubiquinone. Rhodoquinone also enhanced photooxidase activity in photoreaction center preparations from which secondary ubiquinone seemed to have been removed. Rhodoquinone apparently accepts electrons directly from primary ubiquinone during chromatophore photooxidase activity. Rhodoquinone does not participate in the basal activity of photoreaction center preparations, which seems to result from the autooxidation of primary and secondary ubiquinone.

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