Download MendeleyThe Solvent-Exposed Fe-S D-Cluster Contributes to Oxygen-Resistance inDesulfovibrio vulgarisNi-Fe Carbon Monoxide Dehydrogenase.
Wittenborn, E.C., Guendon, C., Merrouch, M., Benvenuti, M., Fourmond, V., Leger, C., Drennan, C.L., Dementin, S.(2020) ACS Catal 10: 7328-7335
- PubMed: 32655979
- DOI: https://doi.org/10.1021/acscatal.0c00934
- Primary Citation of Related Structures:
6VWY, 6VWZ, 6VX0, 6VX1 - PubMed Abstract:
Ni-Fe CO-dehydrogenases (CODHs) catalyze the conversion between CO and CO 2 using a chain of Fe-S clusters to mediate long-range electron transfer. One of these clusters, the D-cluster, is surface-exposed and serves to transfer electrons between CODH and external redox partners. These enzymes tend to be extremely O 2 -sensitive and are always manipulated under strictly anaerobic conditions. However, the CODH from Desulfovibrio vulgaris (Dv) appears unique: exposure to micromolar concentrations of O 2 on the minutes-time scale only reversibly inhibits the enzyme, and full activity is recovered after reduction. Here, we examine whether this unusual property of Dv CODH results from the nature of its D-cluster, which is a [2Fe-2S] cluster, instead of the [4Fe-4S] cluster observed in all other characterized CODHs. To this aim, we produced and characterized a Dv CODH variant where the [2Fe-2S] D-cluster is replaced with a [4Fe-4S] D-cluster through mutagenesis of the D-cluster-binding sequence motif. We determined the crystal structure of this CODH variant to 1.83-Å resolution and confirmed the incorporation of a [4Fe-4S] D-cluster. We show that upon long-term O 2 -exposure, the [4Fe-4S] D-cluster degrades, whereas the [2Fe-2S] D-cluster remains intact. Crystal structures of the Dv CODH variant exposed to O 2 for increasing periods of time provide snapshots of [4Fe-4S] D-cluster degradation. We further show that the WT enzyme purified under aerobic conditions retains 30% activity relative to a fully anaerobic purification, compared to 10% for the variant, and the WT enzyme loses activity more slowly than the variant upon prolonged aerobic storage. The D-cluster is therefore a key site of irreversible oxidative damage in Dv CODH, and the presence of a [2Fe-2S] D-cluster contributes to the O 2 -tolerance of this enzyme. Together, these results relate O 2 -sensitivity with the details of the protein structure in this family of enzymes.
Organizational Affiliation:
Department of Chemistry, Department of Biology, and Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
