title: The naphthoquinol oxidizing cytochrome bc1 complex of the hyperthermophilic knallgasbacterium Aquifex aeolicus: properties and phylogenetic relationships.
abstract: Phylogenetic analysis of constituent proteins of Rieske/cytochrome b complexes [Schütz et al. (2000) J. Mol. Biol. 300, 663-675] indicated that the respective enzyme from the hyperthermophile Aquifex (A.) aeolicus is closely related to proteobacterial counterparts, in disagreement with positioning of its parent species on small subunit rRNA trees. An assessment of the details and possible reasons for this discrepancy necessitates a thorough understanding of the biochemical and biophysical properties of the enzyme in addition to the bioinformatic data. The cytochrome bc(1) complex from A. aeolicus, which is part of the "Knallgasreaction" pathway, was therefore studied in membranes and in detergent-solubilized, isolated complex. Hemes b(L) (E(m,7) = -190 mV; g(z)= 3.7), b(H) (E(m,7) = -60 mV; g(z )= 3.45), and c(1) (E(m,7) = +160 mV; g(z )= 3.55) were identified by EPR and optical spectroscopy in combination with electrochemical methods. Two electrochemically distinct (E(m,7) = +95 mV; E(m,7) = +210 mV) Rieske centers were detected in membranes, and the +210 mV species was shown to correspond to the Rieske center of the cyt bc(1) complex. The gene coding for this latter Rieske protein was heterologously expressed in Escherichia coli, and the resulting protein was characterized in detail. The pool quinone of A. aeolicus was determined to be naphthoquinone. The redox poises of the individual electron-transfer steps are compared to those of other Rieske/cyt b complexes. The Aquifex enzyme was found to represent the only extant naphthoquinol oxidizing true cyt bc(1) complex described so far. An improved scenario for the phylogenetic positioning of the Aquifex cyt bc(1) complex is proposed.
authors.affiliation: Laboratoire de Bioénergétique et Ingénierie des Protéines (UPR9036), CNRS, 31, chemin Joseph-Aiguier, F-13402 Marseille Cedex 20, France.
authors.forename: Michael
authors.initials: M
authors.lastname: Schütz
authors.forename: Barbara
authors.initials: B
authors.lastname: Schoepp-Cothenet
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Lojou
authors.forename: Mireille
authors.initials: M
authors.lastname: Woodstra
authors.forename: Doris
authors.initials: D
authors.lastname: Lexa
authors.forename: Pascale
authors.initials: P
authors.lastname: Tron
authors.forename: Alain
authors.initials: A
authors.lastname: Dolla
authors.forename: Marie-Claire
authors.initials: MC
authors.lastname: Durand
authors.forename: Karl Otto
authors.initials: KO
authors.lastname: Stetter
authors.forename: Frauke
authors.initials: F
authors.lastname: Baymann
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry; D001419:Bacteria / Q000201:enzymology* / Q000235:genetics*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D002462:Cell Membrane / Q000737:chemistry / Q000201:enzymology; D004227:Dithionite / Q000737:chemistry; D004563:Electrochemistry / Q000379:methods; D004578:Electron Spin Resonance Spectroscopy; D014450:Electron Transport Complex III / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D006418:Heme / Q000031:analogs & derivatives / Q000032:analysis; D006873:Hydroquinones / Q000737:chemistry* / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000235:genetics; D010084:Oxidation-Reduction; D010802:Phylogeny; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D013053:Spectrophotometry / Q000379:methods; D017186:Titrimetry
chemical_list: D001426:Bacterial Proteins; D006873:Hydroquinones; D007506:Iron-Sulfur Proteins; D011994:Recombinant Proteins; D004227:Dithionite; D006418:Heme; D014450:Electron Transport Complex III; D001205:Ascorbic Acid