title: Two distinct binding sites for high potential iron-sulfur protein and cytochrome c on the reaction center-bound cytochrome of Rubrivivax gelatinosus.
abstract: The photosynthetic cyclic electron transfer of the purple bacterium Rubrivivax gelatinosus, involving the cytochrome bc(1) complex and the reaction center, can be carried out via two pathways. A high potential iron-sulfur protein (HiPIP) acts as the in vivo periplasmic electron donor to the reaction center (RC)-bound cytochrome when cells are grown under anaerobic conditions in the light, while cytochrome c is the soluble electron carrier for cells grown under (8)aerobic conditions in the dark. A spontaneous reversion of R. gelatinosus C244, a defective mutant in synthesis of the RC-bound cytochrome by insertion of a Km(r) cassette leading to gene disruption with a slow growth rate, restores the normal photosynthetic growth. This revertant, designated C244-P1, lost the Km(r) cassette but synthesized a RC-bound cytochrome with an external 77-amino acid insertion derived from the cassette. We characterized the RC-bound cytochrome of this mutant by EPR, time-resolved optical spectroscopy, and structural analysis. We also investigated the in vivo electron transfer rates between the two soluble electron donors and this RC-bound cytochrome. Our results demonstrated that the C244-P1 RC-bound cytochrome is still able to receive electrons from HiPIP, but it is no longer reducible by cytochrome c(8). Combining these experimental and theoretical protein-protein docking results, we conclude that cytochrome c(8) and HiPIP bind the RC-bound cytochrome at two distinct but partially overlapping sites.
authors.affiliation: Laboratoire de Génétique et Biophysique des Plantes, UMR 6191 CNRS-Commissariat à l'Energie Atomique-Aix-Marseille II, 163 avenue de Luminy, Marseille 13288, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Alric
authors.forename: Makoto
authors.initials: M
authors.lastname: Yoshida
authors.forename: Kenji V P
authors.initials: KV
authors.lastname: Nagashima
authors.forename: Rainer
authors.initials: R
authors.lastname: Hienerwadel
authors.forename: Pierre
authors.initials: P
authors.lastname: Parot
authors.forename: André
authors.initials: A
authors.lastname: Verméglio
authors.forename: Shu-Wen W
authors.initials: SW
authors.lastname: Chen
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Pellequer
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D042521:Burkholderiaceae / Q000378:metabolism*; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism*; D003580:Cytochromes / Q000737:chemistry / Q000378:metabolism; D045304:Cytochromes c / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D005292:Ferricyanides / Q000737:chemistry; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013045:Species Specificity; D013053:Spectrophotometry; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D003574:Cytochrome c Group; D003580:Cytochromes; D005292:Ferricyanides; D007506:Iron-Sulfur Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; C007943:high potential iron-sulfur protein; C007931:hexacyanoferrate III; D045304:Cytochromes c; C017167:cytochrome C(551); D010100:Oxygen