Anaerobic nitric oxide reductase; uses NADH to detoxify nitric oxide (NO), protecting several 4Fe-4S NO-sensitive enzymes. Has at least 2 reductase partners, only one of which (NorW, flavorubredoxin reductase) has been identified. NO probably binds to the di-iron center; electrons enter from the NorW at rubredoxin and are transferred sequentially to the FMN center and the di-iron center. Also able to function as an aerobic oxygen reductase. Binds 3 Fe cations per monomer. Binds 1 FMN per monomer. Nitrogen metabolism; nitric oxide reduction. Homotetramer. In the N-terminal section; belongs to the zinc metallo-hydrolase group 3 family.