Carbon monoxide dehydrogenase reaction mechanism: a likely case of abnormal CO2 insertion to a Ni-H(-) bond.
Ni-containing carbon monoxide dehydrogenases (CODH), present in many anaerobic microorganisms, catalyze the reversible oxidation of CO to CO(2) at the so-called C-cluster. This atypical active site is composed of a [NiFe(3)S(4)] cluster and a single unusual iron ion called ferrous component II or Fe(u) that is bridged to the cluster via one sulfide ion. After additional refinement of recently published high-resolution structures of COOH(x)-, OH(x)-, and CN-bound CODH from Carboxydothermus hydrogenoformans (Jeoung and Dobbek Science 2007, 318, 1461-1464; J. Am. Chem. Soc. 2009, 131, 9922-9923), we have used computational methods on the predominant resulting structures to investigate the spectroscopically well-characterized catalytic intermediates, C(red1) and the two-electron more-reduced C(red2). Several models were geometry-optimized for both states using hybrid quantum mechanical/molecular mechanical potentials. The comparison of calculated Mössbauer parameters of these active site models with experimental data allows us to propose that the C(red1) state has a Fe(u)-Ni(2+) bridging hydroxide ligand and the C(red2) state has a hydride terminally bound to Ni(2+). Using our combined structural and theoretical data, we put forward a revised version of an earlier proposal for the catalytic cycle of Ni-containing CODH (Volbeda and Fontecilla-Camps Dalton Trans. 2005, 21, 3443-3450) that agrees with available spectroscopic and structural data. This mechanism involves an abnormal CO(2) insertion into the Ni(2+)-H(-) bond.
Laboratoire de Cristallographie et de Cristallogenèse des Protéines, Institut de Biologie Structurale J.P. Ebel CEA, CNRS, Université Joseph Fourier 41, rue Jules Horowitz, 38027 Grenoble, France. patricia.amara@ibs.fr
Patricia
P
Amara
Jean-Marie
JM
Mouesca
Anne
A
Volbeda
Juan C
JC
Fontecilla-Camps
D000445:Aldehyde Oxidoreductases / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry*; D002384:Catalysis; D020134:Catalytic Domain; D006859:Hydrogen / Q000737:chemistry*; D009097:Multienzyme Complexes / Q000737:chemistry*; D009532:Nickel / Q000737:chemistry*; D015204:Spectroscopy, Mossbauer
D009097:Multienzyme Complexes; D002245:Carbon Dioxide; D009532:Nickel; D006859:Hydrogen; D000445:Aldehyde Oxidoreductases; C019823:carbon monoxide dehydrogenase