COMPUTATIONAL CHARACTERIZATION OF THE ELUSIVE C-CLUSTER OF CARBON MONOXIDE DEHYDROGENASE

Structural features of the C-cluster of carbon monoxide dehydrogenases at different redox states have been investigated by the density functional theory. The key species involved in the oxidation of CO at clusters C, C(ox), C(red1), C(red2), and C(int), have been specified. Computational results indicate that the CO-induced transformation of the [Ni-4Fe-5S] cluster C into the [Ni-4Fe-4S] cluster is facile energetically, and such structural conversion at the active site may reconcile different reported crystal structures of cluster C. The coordination of CO to the Ni site of the reduced C-cluster (C(red1)) will enhance its electron accommodation ability and makes Fe1 more accessible to other substrates, which lends support to the assumption that C(red1) is a ready state for CO oxidation. On the basis of calculations, the possible catalytic cycle for the oxidation of CO at cluster C was proposed.