期刊
BIOCHEMISTRY
卷 48, 期 31, 页码 7432-7440出版社
AMER CHEMICAL SOC
DOI: 10.1021/bi900574h
关键词
-
资金
- NIH [GM69857, GM39451]
- MIT Energy Initiative
Nickel-containing carbon monoxide dehydrogenases (CODHs) reversibly catalyze the oxidation of carbon monoxide to carbon dioxide and are of vital importance in the global carbon cycle. The unusual catalytic CODH C-cluster has been crystallographically characterized as either a NiFe4S4 or a NiFe4S5 metal center, the latter containing a fifth, additional Sulfide that bridges Ni and a unique Fe site. To determine whether this bridging sulfide is catalytically relevant and to further explore the mechanism of the C-cluster, we obtained crystal structures of the 310 kDa bifunctional CODH/acetyl-CoA synthase complex from Moorella thermoacetica bound both with I substrate H2O/OH- molecule and with a cyanide inhibitor. X-ray diffraction data were collected from native crystals and from identical crystals soaked in a solution containing potassium cyanide. In both structures, the substrate H2O/OH- molecule exhibits binding to the unique Fe site of the C-cluster. We also observe cyanide binding in a bent conformation to Ni of the C-cluster, adjacent the substrate H2O/OH- molecule. Importantly, the bridging sulfide is not present in either structure. As these forms of the C-cluster represent the coordination environment immediately before the reaction takes place, Our Findings do not support a fifth, bridging sulfide playing a catalytic role in the enzyme mechanism. The crystal Structures presented here, along with recent structures of CODHs from other organisms, have led LIS toward a unified mechanism for CO oxidation by the C-cluster, the catalytic center of an environmentally important enzyme.
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