2 H2O + NH4(+) + 6 oxidized [2Fe-2S]-[ferredoxin] = 8 H(+) + nitrite + 6 reduced [2Fe-2S]-[ferredoxin] Binds 1 siroheme per subunit. Binds 1 [4Fe-4S] cluster per subunit. Nitrogen metabolism; nitrate reduction (assimilation). Monomer. Highest expression in roots and hypocotyls. Some expression in cotyledonary whorls. Strong induction by nitrate in roots and hypocotyls. Strong induction by light and weak induction by nitrate in cotyledonary whorls. Belongs to the nitrite and sulfite reductase 4Fe-4S domain family.