NarXNarL
NarXNarL is a bacterial two-component regulatory system consisting of NarX, a membrane-bound sensor histidine kinase, and NarL, a cytosolic response regulator. The system senses nitrate in the environment and coordinates gene expression to enable anaerobic nitrate respiration when oxygen is limited. In many bacteria, NarX detects extracellular nitrate and autophosphorylates on a histidine residue. The phosphate is transferred to NarL, and NarL-P (the phosphorylated form) binds promoter regions to modulate transcription of genes involved in nitrate and nitrite reduction, as well as related transport and regulatory components.
The NarXNarL regulon typically includes operons encoding the nitrate reductase enzymes, such as narGHJI for the
Structural and functional features include NarX’s sensor domains and histidine kinase activity, and NarL’s receiver and