Crystallographic snapshots of cyanide- and water-bound C-clusters from bifunctional carbon monoxide dehydrogenase/acetyl-CoA synthase

Yan Kung, Tzanko I. Doukov, Javier Seravalli, Stephen W. Ragsdale, Catherine L. Drennan

Research output: Contribution to journalArticle

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Abstract

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 NiFe4S 4 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 a 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 substrateH2O/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 us toward a unified mechanism for CO oxidation by the C-cluster, the catalytic center of an environmentally important enzyme.

Original languageEnglish (US)
Pages (from-to)7432-7440
Number of pages9
JournalBiochemistry
Volume48
Issue number31
DOIs
StatePublished - Aug 11 2009

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carbon monoxide dehydrogenase
Acetyl Coenzyme A
Cyanides
Sulfides
Water
Carbon Monoxide
Molecules
Moorella
Crystal structure
Potassium Cyanide
Carbon Cycle
Oxidation
Crystals
Substrates
Enzymes
Nickel
Carbon Dioxide
X-Ray Diffraction
Conformations
Carbon

ASJC Scopus subject areas

  • Biochemistry

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Crystallographic snapshots of cyanide- and water-bound C-clusters from bifunctional carbon monoxide dehydrogenase/acetyl-CoA synthase. / Kung, Yan; Doukov, Tzanko I.; Seravalli, Javier; Ragsdale, Stephen W.; Drennan, Catherine L.

In: Biochemistry, Vol. 48, No. 31, 11.08.2009, p. 7432-7440.

Research output: Contribution to journalArticle

Kung, Yan ; Doukov, Tzanko I. ; Seravalli, Javier ; Ragsdale, Stephen W. ; Drennan, Catherine L. / Crystallographic snapshots of cyanide- and water-bound C-clusters from bifunctional carbon monoxide dehydrogenase/acetyl-CoA synthase. In: Biochemistry. 2009 ; Vol. 48, No. 31. pp. 7432-7440.
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