title: Catalytic cycles for the reduction of [UO2]2+ by cytochrome c7 proteins proposed from DFT calculations.
abstract: The mechanism of the reduction of the hydrated uranyl cation, [UO2](2+), by the cytochromes G. sulfurreducens and D. acetoxidans has been studied using density functional theory calculations. We propose that the initial electron transfer step from the heme is to a cation-cation complex in the case of D. acetoxidans, but for G. sulfurreducens, it is to a single uranyl cation, which then forms a U(V)-U(VI) complex with a second uranyl cation. For both enzymes, the subsequent catalytic pathways are very similar. A U(V)-U(V) complex is formed, which then undergoes disproportionation via two successive protonation steps of one uranyl group, to give a U(VI)-U(IV) complex which dissociates to individual U(VI) and U(IV) species, the former being bound at the enzyme active site. Intermediate structures along the catalytic pathway are consistent with EXAFS data.
authors.affiliation: School of Chemistry, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Mahesh
authors.initials: M
authors.lastname: Sundararajan
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Campbell
authors.forename: Ian H
authors.initials: IH
authors.lastname: Hillier
mesh_terms: D002384:Catalysis; D003574:Cytochrome c Group / Q000378:metabolism*; D045287:Desulfuromonas / Q000201:enzymology; D004579:Electron Transport; D045302:Geobacter / Q000201:enzymology; D006418:Heme / Q000737:chemistry; D017974:Uranium Compounds / Q000737:chemistry / Q000378:metabolism*
chemical_list: D003574:Cytochrome c Group; D017974:Uranium Compounds; C114913:cytochrome C7; D006418:Heme; C012597:uranium dioxide