Photo-induced electron transfer in intact cells of Rubrivivax gelatinosus mutants deleted in the RC-bound tetraheme cytochrome: Insight into evolution of photosynthetic electron transport

• Published in: Biochimica et biophysica acta 2012-05, Vol.1817 (5), p.689-696
• Main Authors: Verméglio, André, Nagashima, Sakiko, Alric, Jean, Arnoux, Pascal, Nagashima, Kenji V.P.
• Format: Article
• Language: English
• Subjects: absorption; Absorption - radiation effects; anaerobic conditions; bacteria; Bacterial Proteins - metabolism; Betaproteobacteria - cytology; Betaproteobacteria - growth & development; Betaproteobacteria - radiation effects; cyt c8; Cytochromes - metabolism; Electron Spin Resonance Spectroscopy; electron transfer; Electron Transport - radiation effects; Electrons; evolution; Evolution, Molecular; Gene Deletion; Heme - metabolism; HIPIP; Light; Models, Molecular; mutants; Mutation - genetics; photosynthesis; Photosynthesis - genetics; Photosynthesis - radiation effects; Photosynthetic bacteria; Photosynthetic Reaction Center Complex Proteins - metabolism; Protein Binding - radiation effects; Rubrivivax gelatinosus; Time Factors
• ISSN: 0005-2728; 0006-3002; 1879-2650
• DOI: 10.1016/j.bbabio.2012.01.011

Deletion of two of the major electron carriers, the reaction center-bound tetrahemic cytochrome and the HiPIP, involved in the light-induced cyclic electron transfer pathway of the purple photosynthetic bacterium, Rubrivivax gelatinosus, significantly impairs its anaerobic photosynthetic growth. Analysis on the light-induced absorption changes of the intact cells of the mutants shows, however, a relatively efficient photo-induced cyclic electron transfer. For the single mutant lacking the reaction center-bound cytochrome, we present evidence that the electron carrier connecting the reaction center and the cytochrome bc1 complex is the High Potential Iron–sulfur Protein. In the double mutant lacking both the reaction center-bound cytochrome and the High Potential Iron–sulfur Protein, this connection is achieved by the high potential cytochrome c8. Under anaerobic conditions, the halftime of re-reduction of the photo-oxidized primary donor by these electron donors is 3 to 4 times faster than the back reaction between P+ and the reduced primary quinone acceptor. This explains the photosynthetic growth of these two mutants. The results are discussed in terms of evolution of the type II RCs and their secondary electron donors. ► We deleted two major electron carriers, RC-bound tetraheme and HiPIP, of Rubrivivax gelatinosus. ► These mutants still grow under anaerobic photosynthetic conditions. ► The electron donor to the RC is HiPIP in the mutant deleted in RC-bound tetraheme. ► The electron donor to the reaction center is the cytochrome c8 in the double mutant.