Terminal reductase that allows anaerobic growth on chlorate as the sole respiratory oxidant. AH2 + chlorate = A + chlorite + H2O Binds 1 [4Fe-4S] cluster. Binds 1 molybdenum-bis(molybdopterin guanine dinucleotide) (Mo-bis-MGD) cofactor per subunit. Heterotrimer of alpha, beta and gamma subunits. Predicted to be exported by the Tat system. The position of the signal peptide cleavage has not been experimentally proven. Has potential use in bioremediation of waste sites contaminated with chlorate, such as pulp and paper industry wastewater. Belongs to the prokaryotic molybdopterin-containing oxidoreductase family.