Membrane-bound cytochrome cz couples quinol oxidoreductase to the P840 reaction center complex in isolated membranes of the green sulfur bacterium Chlorobium tepidum. 1998

H Oh-oka, and M Iwaki, and S Itoh
Department of Biology, Graduate School of Science, Osaka University, Japan. ohoka@bio.sci.osaka-u.ac.jp

The reaction of quinol oxidoreductase and membrane-bound c-type cytochromes was studied in chlorosome-depleted membranes isolated from Chlorobium tepidum. Rapid oxidations of c-type cytochromes were detected after flash excitation. Their re-reductions occurred in parallel with the reduction of cytochrome b, especially in the presence of antimycin A, whereas reductions of both cytochromes c and b were suppressed by added stigmatellin. These results indicate the tight coupling between the photosynthetic reaction center and quinol oxidoreductase. Turnovers of two types of cytochromes c were detected. One was assigned to the monoheme-type cytochrome c (designated cytochrome cz), which is known to be tightly bound to the reaction center complex. The other was a new c-type cytochrome, cytochrome c-556, which functions the same as cytochrome c1. The steps of electron-transfer scheme, menaquinol --> Rieske FeS center --> cytochrom c-556 --> cytochrome cz --> P840, are estimated to have reaction times of 20 ms and 560, 150, and 40 microseconds, respectively. We conclude that quinol oxidoreductase and the reaction center complex in Chlorobium tepidum are linked by two distinct membrane-bound cytochromes, cz and c-556, with no involvement of water-soluble cytochromes.

UI MeSH Term Description Entries
D010084 Oxidation-Reduction A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471). Redox,Oxidation Reduction
D010777 Photochemistry A branch of physical chemistry which studies chemical reactions, isomerization and physical behavior that may occur under the influence of visible and/or ultraviolet light. Photochemistries
D002462 Cell Membrane The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells. Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D003573 Cytochrome b Group Cytochromes (electron-transporting proteins) with protoheme (HEME B) as the prosthetic group. Cytochromes Type b,Cytochromes, Heme b,Group, Cytochrome b,Heme b Cytochromes,Type b, Cytochromes,b Cytochromes, Heme,b Group, Cytochrome
D003574 Cytochrome c Group A group of cytochromes with covalent thioether linkages between either or both of the vinyl side chains of protoheme and the protein. (Enzyme Nomenclature, 1992, p539) Cytochromes Type c,Group, Cytochrome c,Type c, Cytochromes
D004579 Electron Transport The process by which ELECTRONS are transported from a reduced substrate to molecular OXYGEN. (From Bennington, Saunders Dictionary and Encyclopedia of Laboratory Medicine and Technology, 1984, p270) Respiratory Chain,Chain, Respiratory,Chains, Respiratory,Respiratory Chains,Transport, Electron
D000968 Antimycin A An antibiotic substance produced by Streptomyces species. It inhibits mitochondrial respiration and may deplete cellular levels of ATP. Antimycin A1 has been used as a fungicide, insecticide, and miticide. (From Merck Index, 12th ed) Butanoic acid, 2(or 3)-methyl-, 3-((3-(formylamino)-2-hydroxybenzoyl)amino)-8-hexyl-2,6-dimethyl-4,9-dioxo-1,5-dioxonan-7-yl ester,Antimycin A1
D001665 Binding Sites The parts of a macromolecule that directly participate in its specific combination with another molecule. Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining
D013053 Spectrophotometry The art or process of comparing photometrically the relative intensities of the light in different parts of the spectrum.
D014450 Electron Transport Complex III A multisubunit enzyme complex that contains CYTOCHROME B GROUP; CYTOCHROME C1; and iron-sulfur centers. It catalyzes the oxidation of ubiquinol to UBIQUINONE, and transfers the electrons to CYTOCHROME C. In MITOCHONDRIA the redox reaction is coupled to the transport of PROTONS across the inner mitochondrial membrane. Complex III,Cytochrome bc1 Complex,Ubiquinol-Cytochrome-c Reductase,Coenzyme Q-Cytochrome-c Reductase,Coenzyme QH2-Cytochrome-c Reductase,Core I Protein, UCCreductase,Core I Protein, Ubiquinol-Cytochrome c Reductase,Core II Protein, UCCreductase,Core II Protein, Ubiquinol-Cytochrome c Reductase,Cytochrome b-c2 Oxidoreductase,Cytochrome bc1,Dihydroubiquinone-Cytochrome-c Reductase,QH(2)-Cytochrome-c Reductase,QH(2)-Ferricytochrome-c Oxidoreductase,Ubihydroquinone-Cytochrome-c Reductase,Ubiquinol-Cytochrome c Reductase,Ubiquinone-Cytochrome b-c2 Oxidoreductase,Coenzyme Q Cytochrome c Reductase,Coenzyme QH2 Cytochrome c Reductase,Core I Protein, Ubiquinol Cytochrome c Reductase,Core II Protein, Ubiquinol Cytochrome c Reductase,Cytochrome b c2 Oxidoreductase,Dihydroubiquinone Cytochrome c Reductase,Reductase, Ubiquinol-Cytochrome c,Ubihydroquinone Cytochrome c Reductase,Ubiquinol Cytochrome c Reductase,Ubiquinone Cytochrome b c2 Oxidoreductase

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