The pathway of cyclic electron transport in chromatophores of Chromatium vinosum. Evidence for a Q-cycle mechanism |
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| Institution: | 1. Department of Biophysics, Huygens Laboratory of the State University, PO Box 9504, 2300 RA Leiden The Netherlands;2. Department of Biophysics, Physics Laboratory of the Free University, De Boelelann 1081, 1081 HV Amsterdam The Netherlands;1. College of Environmental Science and Engineering, Hunan University, Changsha, 410082, PR China;2. Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Hunan University, Changsha, 410082, PR China;1. Department of Agrifood Production and Environmental Sciences, University of Florence, via Maragliano 77, 50144, Florence, Italy;2. Institute of Chemistry of Organometallic Compounds (ICCOM), CNR, Via Madonna del Piano, 10-50019 Sesto Fiorentino, Florence, Italy;3. Institute of Ecosystem Study (ISE), CNR, Via Madonna del Piano, 10-50019 Sesto Fiorentino, Florence, Italy |
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| Abstract: | Chromatophores of the purple sulfur bacterium Chromatium vinosum were shown to contain a cytochrome similar to cytochrome c1 and two b cytochromes. Cytochrome b can be accumulated in the reduced form upon illumination at an ambient redox potential of +415 mV in the presence of the electron transport inhibitors antimycin A or HOQNO. The reductions of cytochrome b, of the high-potential cytochrome c555 and of the primary electron donor P-870 are all inhibited by myxothiazol. Dark-adapted C. vinosum chromatophores show little cytochrome b reduction on the first flash. Considerable cytochrome b reduction (1 cytochrome b:8 P-870 present) is observed on the second flash. This observation and the 1:1 stoichiometry observed between cytochrome b reduction and P-870+ reduction after the second flash support a Q-cycle model for cyclic electron flow in C. vinosum. |
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