The Solvent-Exposed Fe–S D-Cluster Contributes to Oxygen-Resistance in Desulfovibrio vulgaris Ni–Fe Carbon Monoxide Dehydrogenase

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-timescale 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 1

Revealing redox isomerism in trichromium imides by anomalous diffraction

“…[10][11][12][13] Understanding how the geometry of a polynuclear cluster impacts delocalization is especially relevant as recent advances in the chemistry and crystallography of polynuclear biological active sites have proven that structural rearrangements are key to the function of FeMoco and the (OEC) of photosystem II, among others. [14][15][16][17][18][19] Such rearrangements impact not only the docking and reactivity of substrates at the enzyme active sites, but also the pathways for electronic delocalization between the constituent metal atoms. Thus, furthering our knowledge of the relationship between geometry and delocalization in polynuclear transition metal clusters is not just a matter of fundamental scientific interest but also highly relevant to our understanding of biological active sites.…”

Efficient Electrochemical CO2/CO Interconversion by an Engineered Carbon Monoxide Dehydrogenase on a Gas-Diffusion Carbon Nanotube-Based Bioelectrode

“…For comparison, the only other CODH studied at nanostructured electrode towards electrocatalytic CO2 reduction is ChCODH-I which was immobilized at nanostructured silver-nanocluster-modified TiO2 electrodes and achieved maximum current density of 0.26 mA cm -2 . 12 Other types of metal-based nanomaterials such as CNTsupported copper phtalocyanines 59 reaches 6.9 mA cm -2 at 300 mV overpotential while, in the case of mesoporous gold-based electrodes, 60 22 mA cm -2 can be reached at 240 mV overpotential. These results show that Rec-RrCODH CTJ -modified MWCNT ADA electrodes are closed to the best metal-based and molecular-based catalysts in terms of current densities.…”

Electrochemical Studies of CO2‐Reducing Metalloenzymes

“…Dv CODH is in fact so resistant to O 2 that it is possible to purify the enzyme aerobically [43] (with only a 70 % loss of specific activity); this feature is apparently related to the nature of the D cluster of Dv CODH. This cluster is a [2Fe2S] cluster unlike in the other characterized CODHs, which have a [4Fe4S] cluster.…”

“…This cluster is a [2Fe2S] cluster unlike in the other characterized CODHs, which have a [4Fe4S] cluster. Replacement of the [2Fe2S] cluster with a [4Fe4S] in Dv CODH led to a drastically decreased activity after aerobic purification, but almost no change in the anaerobically purified enzyme [43] …”