title: Structure of superoxide reductase bound to ferrocyanide and active site expansion upon X-ray-induced photo-reduction.
abstract: Some sulfate-reducing and microaerophilic bacteria rely on the enzyme superoxide reductase (SOR) to eliminate the toxic superoxide anion radical (O2*-). SOR catalyses the one-electron reduction of O2*- to hydrogen peroxide at a nonheme ferrous iron center. The structures of Desulfoarculus baarsii SOR (mutant E47A) alone and in complex with ferrocyanide were solved to 1.15 and 1.7 A resolution, respectively. The latter structure, the first ever reported of a complex between ferrocyanide and a protein, reveals that this organo-metallic compound entirely plugs the SOR active site, coordinating the active iron through a bent cyano bridge. The subtle structural differences between the mixed-valence and the fully reduced SOR-ferrocyanide adducts were investigated by taking advantage of the photoelectrons induced by X-rays. The results reveal that photo-reduction from Fe(III) to Fe(II) of the iron center, a very rapid process under a powerful synchrotron beam, induces an expansion of the SOR active site.
authors.affiliation: LCCP, UMR 5075, IBS-CEA/CNRS/Université J. Fourier, 41 Avenue Jules Horowitz, 38027 Grenoble, Cedex 1, France.
authors.forename: Virgile
authors.initials: V
authors.lastname: Adam
authors.forename: Antoine
authors.initials: A
authors.lastname: Royant
authors.forename: Vincent
authors.initials: V
authors.lastname: Nivière
authors.forename: Fernando P
authors.initials: FP
authors.lastname: Molina-Heredia
authors.forename: Dominique
authors.initials: D
authors.lastname: Bourgeois
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D003901:Desulfovibrio / Q000201:enzymology; D005295:Ferrocyanides / Q000737:chemistry* / Q000378:metabolism; D008027:Light; D046911:Macromolecular Substances; D008958:Models, Molecular; D009154:Mutation; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013481:Superoxides / Q000737:chemistry; D014965:X-Rays
chemical_list: D001426:Bacterial Proteins; D005295:Ferrocyanides; D046911:Macromolecular Substances; D013481:Superoxides; D010088:Oxidoreductases; C121849:superoxide reductase; C020354:hexacyanoferrate II