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Publication Abstract from PubMed

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.

Structure of superoxide reductase bound to ferrocyanide and active site expansion upon X-ray-induced photo-reduction.,Adam V, Royant A, Niviere V, Molina-Heredia FP, Bourgeois D Structure. 2004 Sep;12(9):1729-40. PMID:15341736^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.