Microbial oxidative sulfur metabolism: biochemical evidence of the membrane-bound heterodisulfide reductase-like complex of the bacterium Aquifex aeolicus.
The Hdr (heterodisulfide reductase)-like enzyme is predicted, from gene transcript profiling experiments previously published, to be essential in oxidative sulfur metabolism in a number of bacteria and archaea. Nevertheless, no biochemical and physicochemical data are available so far about this enzyme. Genes coding for it were identified in Aquifex aeolicus, a Gram-negative, hyperthermophilic, chemolithoautotrophic and microaerophilic bacterium that uses inorganic sulfur compounds as electron donor to grow. We provide biochemical evidence that this Hdr-like enzyme is present in this sulfur-oxidizing prokaryote (cultivated with thiosulfate or elemental sulfur). We demonstrate, by immunolocalization and cell fractionation, that Hdr-like enzyme is associated, presumably monotopically, with the membrane fraction. We show by co-immunoprecipitation assay or partial purification, that the Hdr proteins form a stable complex composed of at least five subunits, HdrA, HdrB1, HdrB2, HdrC1 and HdrC2, present in two forms of high molecular mass on native gel (∼240 and 450 kDa). These studies allow us to propose a revised model for dissimilatory sulfur oxidation pathways in A. aeolicus, with Hdr predicted to generate sulfite.
Aix Marseille Univ, CNRS, BIP UMR7281, 13402 Marseille, France.
Souhela
S
Boughanemi
Aix Marseille Univ, CNRS, BIP UMR7281, 13402 Marseille, France.
Jordan
J
Lyonnet
Aix Marseille Univ, CNRS, BIP UMR7281, 13402 Marseille, France.
Pascale
P
Infossi
Aix Marseille Univ, CNRS, Fermentation Plant Unit, FR 3479, 13402 Marseille, France.
Marielle
M
Bauzan
Aix Marseille Univ, CNRS, Microscopy platform, FR 3479, 13402 Marseille, France.
Artémis
A
Kosta
Aix Marseille Univ, CNRS, Proteomic platform, FR 3479, 13402 Marseille, France.
Sabrina
S
Lignon
Aix Marseille Univ, CNRS, BIP UMR7281, 13402 Marseille, France.
Marie-Thérèse
MT
Giudici-Orticoni
Aix Marseille Univ, CNRS, BIP UMR7281, 13402 Marseille, France guiral@imm.cnrs.fr.
Marianne
M
Guiral
D001419:Bacteria / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D052837:Chemoautotrophic Growth; D008565:Membrane Proteins / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D013455:Sulfur / Q000378:metabolism*
D001426:Bacterial Proteins; D008565:Membrane Proteins; D013455:Sulfur; D010088:Oxidoreductases; C087171:heterodisulfide reductase
Aquifex aeolicus; chemolithotrophe; heterodisulfide reductase (Hdr)-like enzyme; oxidation of dissimilatory sulfur compounds; sulfite dehydrogenase