Cysteine 295 indirectly affects Ni coordination of carbon monoxide dehydrogenase-II C-cluster

A unique [Ni-Fe-S] cluster (C-cluster) constitutes the active center of Ni-containing carbon monoxide dehydrogenases (CODHs). His261, which coordinates one of the Fe atoms with Cys295, is suggested to be the only residue required for Ni coordination in the C-cluster. To evaluate the role of Cys295, we constructed CODH-II variants. Ala substitution for the Cys295 substitution resulted in the decrease of Ni content and didn't result in major change of Fe content. In addition, the substitution had no effect on the ability to assemble a full complement of [Fe-S] clusters. This strongly suggests Cys295 indirectly and His261 together affect Ni-coordination in the C-cluster.