Carbon Dioxide Activation at the Ni,Fe-Cluster of Anaerobic Carbon Monoxide Dehydrogenase

Abstract

Anaerobic CO dehydrogenases catalyze the reversible oxidation of CO to CO2 at a complex Ni-, Fe-, and S-containing metal center called cluster C. We report crystal structures of CO dehydrogenase II from Carboxydothermus hydrogenoformans in three different states. In a reduced state, exogenous CO2 supplied in solution is bound and reductively activated by cluster C. In the intermediate structure, CO2 acts as a bridging ligand between Ni and the asymmetrically coordinated Fe, where it completes the square-planar coordination of the Ni ion. It replaces a water/hydroxo ligand bound to the Fe ion in the other two states. The structures define the mechanism of CO oxidation and CO2 reduction at the Ni-Fe site of cluster C.

Structure of the α 2 ε 2 Ni-dependent CO dehydrogenase component of the Methanosarcina barkeri acetyl-CoA decarbonylase/synthase complex

“…Structural support for this hypothesis has recently come from Jeong and Dobbek (26), who report the structures of the C. hydrogenoformans at three different states, including one that contains bound CO 2 . Notably, the C clusters in these C. hydrogenoformans Ni-CODH structures have no bridging sulfide and instead harbor a bound H 2 O/OH Ϫ or, in the case of the CO 2 -treated protein, a CO 2 molecule that bridges the Ni and exogenous FCII iron with the carbon of CO 2 binding the Ni atom.…”

Kinetics and mechanistic analysis of an extremely rapid carbon dioxide fixation reaction

“…nickel hydroxide | carbon dioxide-bicarbonate conversion | reaction mechanism R ecent research in this laboratory has been directed toward the attainment of synthetic analogues of the NiFe 3 S 4 active site of the enzyme carbon monoxide dehydrogenase (1,2), which catalyzes the interconversion reaction CO 2 þ 2H þ þ 2e − ⇌ CO þ H 2 O. In the course of this work, we have prepared binuclear Ni II ∕Fe II bridged species with the intention of simulating the Ni…Fe component of the enzyme site that is the locus of substrate binding, activation, and product release (3).…”

A Simple, Large-Scale Overexpression Method of Deriving Carbon Monoxide Dehydrogenase II from Thermophilic BacteriumCarboxydothermus hydrogenoformans

“…5,6) Recently, the expression system for cooS II gene encoding CODH II from C. hydrogenoformans in E. coli was reported. 7,8) Notably, recombinant CODH II (Rec-CODH II) shows CO oxidation activity nearly equal to native CODH II. 7,8) This culture process, however, poses a critical problem: the system inevitably produces hydrogen sulfide derived from Na 2 S, which is a sulfide source for [Fe-S] clusters and a reductant for the reduction of the medium.…”

“…7,8) Notably, recombinant CODH II (Rec-CODH II) shows CO oxidation activity nearly equal to native CODH II. 7,8) This culture process, however, poses a critical problem: the system inevitably produces hydrogen sulfide derived from Na 2 S, which is a sulfide source for [Fe-S] clusters and a reductant for the reduction of the medium. Hydrogen sulfide is known to be toxic and to have a corrosive effect on metallic equipment, and hence the culture method is not suitable for large-scale culture.…”