Dimethyl sulfoxide (DMSO) reductase catalyzes the reduction of dimethyl sulfoxide (DMSO) to dimethyl sulfide (DMS) during anaerobic respiration; it can also use trimethylamine N-oxide (TMAO) as terminal electron acceptor. Required for anaerobic respiration on DMSO and TMAO; subunit A is proposed to be catalytically active. a menaquinone + dimethyl sulfide + H2O = a menaquinol + dimethyl sulfoxide Binds 1 molybdenum-bis(molybdopterin guanine dinucleotide) (Mo-bis-MGD) cofactor per subunit. Binds 1 [4Fe-4S] cluster. Probable multiprotein complex that likely consists of DmsA, DmsB and DmsC. By anaerobic conditions. Its expression is under the control of DmsR. Predicted to be exported by the Tat system. The position of the signal peptide cleavage has not been experimentally proven. Cells lacking this gene fail to grow under anaerobic conditions using either DMSO or TMAO as terminal electron acceptors. Belongs to the prokaryotic molybdopterin-containing oxidoreductase family.