PDBsum entry 3b51

Oxidoreductase

PDB id

3b51

Contents

			Protein chain

					633 a.a.

			Ligands

					SF4


					FES


					WCC

			Metals

					FE2

			Waters ×884

References listed in PDB file

Key reference

Title

Carbon dioxide activation at the ni,Fe-Cluster of anaerobic carbon monoxide dehydrogenase.

Authors

J.H.Jeoung, H.Dobbek.

Ref.

Science, 2007, 318, 1461-1464. [DOI no: 10.1126/science.1148481]

PubMed id

18048691

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.



	Figure 1. Fig. 1. The –600 mV (A), –600 mV+CO[2] (B) and –320 mV (C) states of cluster C. 2F[obs] – F[calc] maps in blue are contoured at 1 , and F[obs] – F[calc] maps in green are contoured at 4.5 . For the calculation of the F[obs] – F[calc] map, the OH[x] ligand [(A) and (C)] and the CO[2] ligand (B) have been removed from the model. An alternative position found for Fe1, termed Fe1B, is depicted in transparent light gray. The occupancies for the alternative position have been estimated to 10 to 30%. Selected distances are shown in Å. For more details on the geometry of the three states, see figs. S2 to S4. All pictures were prepared by using PyMol (23).		Figure 2. Fig. 2. Superposition of the –600 mV (blue) and –600 mV+CO[2] (element colors) states.

PROCHECK

	Headers