CO-induced structural rearrangement of the C cluster in Carboxydothermus hydrogenoformans CO dehydrogenase - Evidence from Ni K-edge X-ray absorption spectroscopy?

Weiwei Gu, Javier Seravalli, Stephen W. Ragsdale, Stephen P. Cramer

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We have examined the C cluster in type II CO dehydrogenase (CODH) from Carboxydothermus hydrogenformans using Ni K-edge X-ray absorption near edge spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy. The enzyme was studied under three conditions: "as-isolated" and after treatment with CO or Ti1II. The shape of the Ni K-edge changes slightly between the different conditions, but no significant edge shift is seen, suggesting that the C cluster contains NiII in both forms. The Ni EXAFS of as-isolated CODH can be simulated with 4 Ni-S interactions at 2.20 Å with a large spread in distances. A light atom (C, N, O) is not required to fit the spectrum. After CO treatment, significant changes are observed in the EXAFS. A new feature appears at ∼-2.7 Å; this component is consistent with a Ni-Fe interaction. The average Ni-S distance also expands to ∼2.25 Å. The changes between the two forms suggest that the active site (C cluster) undergoes structural rearrangement after CO treatment, and the observed changes help reconcile the two different crystal structures. The implications of the structural change for the enzyme activation and mechanism are discussed.

Original languageEnglish (US)
Pages (from-to)9029-9035
Number of pages7
Issue number28
StatePublished - Jul 20 2004


ASJC Scopus subject areas

  • Biochemistry

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