The nitrate reductase enzyme complex allows E.coli to use nitrate as an electron acceptor during anaerobic growth. The alpha chain is the actual site of nitrate reduction. 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. Dimer of heterotrimers each composed of an alpha, a beta and a gamma chain. Alpha and beta are catalytic chains; gamma chains are involved in binding the enzyme complex to the cytoplasmic membrane. Interacts with the NarJ chaperone. By nitrate. Apoenzyme contains at least 2 NarJ-binding sites, one interfering with membrane anchoring and another being involved in molybdenum insertion. The first binding-site is a short peptide sequence near the N-terminus that contains a twin-arginine homologous motif. Belongs to the prokaryotic molybdopterin-containing oxidoreductase family.