title: Two molecules of cytochrome c function as the electron donors to P840 in the reaction center complex isolated from a green sulfur bacterium, Chlorobium tepidum.
abstract: A photoactive reaction center complex was isolated from a thermophilic green sulfur bacterium, Chlorobium tepidum under anaerobic conditions. The electron transfer occurred from heme c to the photo-oxidized reaction center chlorophyll, P840+, with a half time (t1/2) of 110 or 340 microseconds at 24 or 12 degrees C, respectively. Optical measurements under multiflash excitations indicated that two hemes function as the immediate electron donors to P840+. SDS-PAGE analysis of the RC complex in combination with the N-terminal amino acid sequence analyses revealed five subunit bands; a core protein (65 kDa), the light harvesting bacteriochlorophyll alpha protein (41 kDa), a protein with 2[4Fe-4S] clusters (31 kDa), monoheme cytochrome c (22 kDa), and a 18-kDa protein whose function is unknown. The reaction center complex, thus, contains two molecules of cytochrome c per P840.
authors.affiliation: Department of Biology, Faculty of Science, Osaka University, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Oh-oka
authors.forename: S
authors.initials: S
authors.lastname: Kamei
authors.forename: H
authors.initials: H
authors.lastname: Matsubara
authors.forename: M
authors.initials: M
authors.lastname: Iwaki
authors.forename: S
authors.initials: S
authors.lastname: Itoh
mesh_terms: D000595:Amino Acid Sequence; D001419:Bacteria / Q000378:metabolism*; D003080:Cold Temperature; D003574:Cytochrome c Group / Q000378:metabolism*; D004579:Electron Transport; D006207:Half-Life; D008027:Light; D045342:Light-Harvesting Protein Complexes; D008954:Models, Biological; D008969:Molecular Sequence Data; D010788:Photosynthesis / Q000502:physiology*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000378:metabolism* / Q000528:radiation effects; D017421:Sequence Analysis; D013053:Spectrophotometry
chemical_list: D003574:Cytochrome c Group; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins