Sensory histidine kinase in two-component regulatory system with NarL; Acts as a sensor for nitrate/nitrite and transduces signal of nitrate availability to the NarL protein and of both nitrate/nitrite to the NarP protein. NarX probably activates NarL and NarP by phosphorylation in the presence of nitrate. NarX also plays a negative role in controlling NarL activity, probably through dephosphorylation in the absence of nitrate.

Sensory histidine kinase in two-component regulatory sytem with UhpA; Part of the UhpABC signaling cascade that controls the expression of the hexose phosphate transporter UhpT. UhpB functions as a membrane-associated protein kinase that autophosphorylates in response to interaction with UhpC, and subsequently transfers its phosphate group to the response regulator UhpA. Can also dephosphorylate UhpA.

Ferredoxin-type protein, role in electron transfer to periplasmic nitrate reductase NapA; Could be involved in the maturation of NapA, the catalytic subunit of the periplasmic nitrate reductase, before its export into the periplasm. Is not involved in the electron transfer from menaquinol or ubiquinol to the periplasmic nitrate reductase.

Nitrite reductase, formate-dependent, cytochrome; Catalyzes the reduction of nitrite to ammonia, consuming six electrons in the process. Has very low activity toward hydroxylamine. Has even lower activity toward sulfite. Sulfite reductase activity is maximal at neutral pH (By similarity).

Putative DNA-binding transcriptional response regulator; Putative regulator; Protein involved in transcription activator activity and transcription.

Response regulator in two-component regulatory system with TorS; Member of the two-component regulatory system TorS/TorR involved in the anaerobic utilization of trimethylamine-N-oxide (TMAO). Phosphorylated TorR activates the transcription of the torCAD operon by binding to four decameric boxes located in the torCAD promoter. Box1, 2 and 4 contain the DNA sequence 5'-CTGTTCATAT-3' and box3 contains the DNA sequence 5'-CCGTTCATCC-3'. Phosphorylated as well as unphosphorylated TorR negatively regulates its own expression by binding to box1 and 2.

Nitrite reductase, large subunit, NAD(P)H-binding; Nitrite reductase (NAD(P)H) subunit; Protein involved in anaerobic respiration; Belongs to the nitrite and sulfite reductase 4Fe-4S domain family.

Aerobic respiration control sensor protein ArcB; Member of the two-component regulatory system ArcB/ArcA. Sensor-regulator protein for anaerobic repression of the arc modulon. Activates ArcA via a four-step phosphorelay. ArcB can also dephosphorylate ArcA by a reverse phosphorelay involving His-717 and Asp-576.

Nitrate reductase, periplasmic, large subunit; Catalytic subunit of the periplasmic nitrate reductase complex NapAB. Receives electrons from NapB and catalyzes the reduction of nitrate to nitrite; Belongs to the prokaryotic molybdopterin-containing oxidoreductase family. NasA/NapA/NarB subfamily.