Catalytic cycles for the reduction of [UO2]2+ by cytochrome c7 proteins proposed from DFT calculations.
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.
Sundararajan
Mahesh
M
School of Chemistry, University of Manchester, Manchester M13 9PL, UK.
Campbell
Andrew J
AJ
Hillier
Ian H
IH
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*
D003574:Cytochrome c Group; D017974:Uranium Compounds; C114913:cytochrome C7; D006418:Heme; C012597:uranium dioxide