title: The aerobic respiratory chain of the acidophilic archaeon Ferroplasma acidiphilum: A membrane-bound complex oxidizing ferrous iron.
abstract: The extremely acidophilic archaeon Ferroplasma acidiphilum is found in iron-rich biomining environments and is an important micro-organism in naturally occurring microbial communities in acid mine drainage. F. acidiphilum is an iron oxidizer that belongs to the order Thermoplasmatales (Euryarchaeota), which harbors the most extremely acidophilic micro-organisms known so far. At present, little is known about the nature or the structural and functional organization of the proteins in F. acidiphilum that impact the iron biogeochemical cycle. We combine here biochemical and biophysical techniques such as enzyme purification, activity measurements, proteomics and spectroscopy to characterize the iron oxidation pathway(s) in F. acidiphilum. We isolated two respiratory membrane protein complexes: a 850 kDa complex containing an aa3-type cytochrome oxidase and a blue copper protein, which directly oxidizes ferrous iron and reduces molecular oxygen, and a 150 kDa cytochrome ba complex likely composed of a di-heme cytochrome and a Rieske protein. We tentatively propose that both of these complexes are involved in iron oxidation respiratory chains, functioning in the so-called uphill and downhill electron flow pathways, consistent with autotrophic life. The cytochrome ba complex could possibly play a role in regenerating reducing equivalents by a reverse ('uphill') electron flow. This study constitutes the first detailed biochemical investigation of the metalloproteins that are potentially directly involved in iron-mediated energy conservation in a member of the acidophilic archaea of the genus Ferroplasma.
authors.affiliation: CNRS, Aix Marseille Université, BIP UMR 7281, FR 3479, 13402 Marseille, France.
authors.forename: Cindy J
authors.initials: CJ
authors.lastname: Castelle
authors.affiliation: CNRS, Aix Marseille Université, BIP UMR 7281, FR 3479, 13402 Marseille, France.
authors.forename: Magali
authors.initials: M
authors.lastname: Roger
authors.affiliation: CNRS, Aix Marseille Université, Unité de Fermentation, FR 3479, 13402 Marseille, France.
authors.forename: Marielle
authors.initials: M
authors.lastname: Bauzan
authors.affiliation: CNRS, Aix Marseille Université, BIP UMR 7281, FR 3479, 13402 Marseille, France.
authors.forename: Myriam
authors.initials: M
authors.lastname: Brugna
authors.affiliation: CNRS, Aix Marseille Université, Plate-forme Protéomique MaP IBiSA, FR 3479, 13402 Marseille, France.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Lignon
authors.affiliation: Helmholtz Centre for Infection Research, 7 Inhoffen Strasse, 38124 Braunschweig, Germany.
authors.forename: Manfred
authors.initials: M
authors.lastname: Nimtz
authors.affiliation: Helmholtz Centre for Infection Research, 7 Inhoffen Strasse, 38124 Braunschweig, Germany; School of Biological Sciences, Deiniol Road, LL57 2UW, Bangor, UK.
authors.forename: Olga V
authors.initials: OV
authors.lastname: Golyshina
authors.affiliation: CNRS, Aix Marseille Université, BIP UMR 7281, FR 3479, 13402 Marseille, France.
authors.forename: Marie-Thérèse
authors.initials: MT
authors.lastname: Giudici-Orticoni
authors.affiliation: CNRS, Aix Marseille Université, BIP UMR 7281, FR 3479, 13402 Marseille, France. Electronic address: guiral@imm.cnrs.fr.
authors.forename: Marianne
authors.initials: M
authors.lastname: Guiral
mesh_terms: D000143:Acids / Q000737:chemistry; D000332:Aerobiosis / Q000502:physiology; D019843:Archaeal Proteins / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism*; D005296:Ferrous Compounds / Q000737:chemistry* / Q000378:metabolism; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism*; D009876:Operon; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D019603:Thermoplasmales / Q000145:classification* / Q000254:growth & development / Q000378:metabolism
chemical_list: D000143:Acids; D019843:Archaeal Proteins; D005296:Ferrous Compounds; D046912:Multiprotein Complexes; D003576:Electron Transport Complex IV; D010100:Oxygen
keywords: Acidophilic archaea; Cytochrome ba complex; Cytochrome oxidase; Ferroplasma; Iron oxidation pathway; Sulfocyanin