title: Diversity of cytochrome bc complexes: example of the Rieske protein in green sulfur bacteria.
abstract: The Rieske 2Fe2S cluster of Chlorobium limicola forma thiosulfatophilum strain tassajara was studied by electron paramagnetic resonance spectroscopy. Two distinct orientations of its g tensor were observed in oriented samples corresponding to differing conformations of the protein. Only one of the two conformations persisted after treatment with 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone. A redox midpoint potential (Em) of +160 mV in the pH range of 6 to 7.7 and a decreasing Em (-60 to -80 mV/pH unit) above pH 7.7 were found. The implications of the existence of differing conformational states of the Rieske protein, as well as of the shape of its Em-versus-pH curve, in green sulfur bacteria are discussed.
authors.affiliation: Laboratoire de Bioénergétique et Ingénierie des Protéines (UPR 9036), Institut de Biologie Structurale et Microbiologie, 13402 Marseille Cedex 20, France.
authors.forename: M
authors.initials: M
authors.lastname: Brugna
authors.forename: D
authors.initials: D
authors.lastname: Albouy
authors.forename: W
authors.initials: W
authors.lastname: Nitschke
mesh_terms: D019414:Chlorobi / Q000737:chemistry*; D003573:Cytochrome b Group / Q000737:chemistry*; D003574:Cytochrome c Group / Q000737:chemistry*; D014450:Electron Transport Complex III; D006863:Hydrogen-Ion Concentration; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy
chemical_list: D003573:Cytochrome b Group; D003574:Cytochrome c Group; D007506:Iron-Sulfur Proteins; C037989:Rieske iron-sulfur protein; D014450:Electron Transport Complex III