The alpha chain is the actual site of nitrate reduction (Probable). Supports anaerobic growth of E.coli on glycerol in an E.coli mutant lacking endogenous nitrate reductase. a quinol + nitrate = a quinone + H2O + nitrite Binds 1 [4Fe-4S] cluster per subunit. Binds 1 molybdenum-bis(molybdopterin guanine dinucleotide) (Mo-bis-MGD) cofactor per subunit. Increased nitrate reductase activity is seen under hypoxic conditions, however this seems to be due to induction of the probable nitrate/nitrite transporter narK2 rather than increased enzyme activity. Constitutively expressed; independent of nitrate and nitrate levels. Loss of nitrate reductase activity in aerobic and hypoxic conditions. One of the activities induced in M.tuberculosis by hypoxia is the dissimilatory reduction of nitrate to nitrite, which serves to provide energy as the bacteria adapt to anaerobiosis. Belongs to the prokaryotic molybdopterin-containing oxidoreductase family.