3I39: Ni,fe-codh-320 Mv+cn State

Carbon monoxide dehydrogenases (CODHs) catalyze the reversible oxidation of carbon monoxide with water to carbon dioxide, two protons, and two electrons. The CODHs of anaerobic microorganisms harbor a complex Ni/Fe/S-containing metal center called a C-cluster in their active site, which activates the substrates water and carbon monoxide, stabilizes an intermediary metal-carboxylate, and transiently stores the two electrons generated in the reaction. Several small molecules have been reported to inhibit carbon monoxide oxidation by CODHs, among which the cyanide anion acts as a slow binding inhibitor. Cyanide is isoelectronic to the substrate carbon monoxide, and its binding to the C-cluster has been reported to involve nickel, nickel and iron, or only iron. We report the crystal structure of CODH-II from Carboxydothermus hydrogenoformans in complex with cyanide at 1.36 A resolution. The structure reveals that cyanide binds to the C-cluster at an open coordination site completing the square-planar coordination geometry of the nickel ion. While active CODH has a water/hydroxo-ligand bound to an iron ion near nickel, in the cyanide complex the water/hydroxo-ligand is lost and iron occupies a position more close to the nickel ion. Based on the structure, we suggest that the competitive inhibitory character of cyanide originates from it obstruction of carbon monoxide binding to the nickel ion while the slow binding inhibition is due to a conformational change of the protein during which the water/hydroxo-ligand bound to iron is lost.
PDB ID: 3I39Download
MMDB ID: 75942
PDB Deposition Date: 2009/6/30
Updated in MMDB: 2009/09
Experimental Method:
x-ray diffraction
Resolution: 1.36  Å
Source Organism:
Similar Structures:
Biological Unit for 3I39: dimeric; determined by author and by software (PISA)
Molecular Components in 3I39
Label Count Molecule
Proteins (2 molecules)
Carbon Monoxide Dehydrogenase 2
Molecule annotation
Chemicals (12 molecules)
* Click molecule labels to explore molecular sequence information.

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