Catalyzes the oxidation of carbon monoxide to carbon dioxide. a quinone + CO + H2O = a quinol + CO2 Binds 1 Cu(+) ion per subunit. Binds 1 Mo-molybdopterin cytosine dinucleotide (Mo-MCD) cofactor per subunit. Dimer of heterotrimers. Each heterotrimer consists of a large, a medium and a small subunit.