Diversity of cytochrome bc complexes: example of the Rieske protein in green sulfur bacteria.
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.
Brugna
M
M
Laboratoire de Bioénergétique et Ingénierie des Protéines (UPR 9036), Institut de Biologie Structurale et Microbiologie, 13402 Marseille Cedex 20, France.
Albouy
D
D
Nitschke
W
W
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
D003573:Cytochrome b Group; D003574:Cytochrome c Group; D007506:Iron-Sulfur Proteins; C037989:Rieske iron-sulfur protein; D014450:Electron Transport Complex III