DMSO reductase

An additional fifth cap-like ligand is the side-chain O of serine-147 residue, further classifying the enzyme as Type III DMSO reductase.

Using S K-edge XAS and DFT, these model studies point to concerted S-O scission and electron transfer.

[8] X-ray crystallography established that the overall tertiary structure of the enzyme remains constant through the reaction progression.

While one x-ray crystallography investigation concluded equidistant coordination of all four Mo-S ligands in the oxidized form, which is supported by numerous x-ray absorption spectroscopy (XAS) studies, a different study characterized asymmetrical Mo-S distances.

This shift in ligand-Mo bond length is consistent with the proposed mechanism of direct oxygen transfer from the DMSO substrate to the Mo.

In the reduction of Mo and protonation of the oxo-group, it is proposed that a cytochrome electron source could bind to a depression above the active site and directly reduce the Mo center, or alternatively this cytochrome could bind to a well-solvated polypeptide loop in proximity to the Q-pterin, and Q-pterin could mediate this electron transfer.

A study of lacZ fusions (reporter genes) to corresponding dorS, dorR, and dorC promoters concluded that expression of DorR and DorC increased in reduced oxygen environments, but DorS expression was unaffected by oxygen concentration.

Cloud formation is a key component in increasing earth's albedo and regulating atmospheric temperature, thus this enzyme and the reaction it catalyzes could prove helpful on the climate control frontier.

The reaction catalyzed by DMSO reductase.
Tertiary structure of DMSOR shows four domains surrounding the active site and cofactors (orange) [ 4 ]
Active site ligand coordination of fully oxidized (Mo VI) DMSOR: two pyranopterindithiolene ligands, a serine-147 residue ligand, and an oxo-group ligand [ 3 ]
Two orientations of active site of fully reduced (Mo IV) DMSOR: red Mo IV core, yellow/orange pyranopterindithiolene-GMP ligand, blue serine-147 residue ligand, pink unbound DMSO substrate [ 5 ]
Proposed catalytic mechanism of DMSO reductase [ 3 ]