Disease relevance of ECs1727

• The regulation of specific gene expression by nitrate in Escherichia coli is mediated by the NarX/NarQ-NarL system [1].
• Biochemical Society Special Lecture. Nitrate- and nitrite-responsive sensors NarX and NarQ of proteobacteria [2].

High impact information on ECs1727

• Phosphorylation and dephosphorylation catalyzed in vitro by purified components of the nitrate sensing system, NarX and NarL [1].
• Incubation of the labeled NarX with purified NarL resulted in the transient phosphorylation of NarL [1].
• The relative stabilities of the phosphorylated forms of the two proteins at different pH values were consistent with the proposal that, in analogy to other related two-component regulatory systems, NarX and NarL were phosphorylated on specific histidine and aspartate residues, respectively [1].
• Nitrate induces a stronger response than nitrite and is effective at lower concentrations, mirroring the relative sensitivity to these ligands exhibited by NarX itself [3].
• Here, we show that a chimeric protein that joins the ligand-binding, transmembrane and linker domains of the NarX sensor kinase to the signalling and adaptation domains of the Tar chemoreceptor of Escherichia coli mediates repellent responses to nitrate and nitrite [3].

Chemical compound and disease context of ECs1727

• Discrimination between structurally related ligands nitrate and nitrite controls autokinase activity of the NarX transmembrane signal transducer of Escherichia coli K-12 [4].
• Hierarchical control of anaerobic gene expression in Escherichia coli K-12: the nitrate-responsive NarX-NarL regulatory system represses synthesis of the fumarate-responsive DcuS-DcuR regulatory system [5].

Biological context of ECs1727

• Both were also trans dominant over the NarX P-box mutant which conferred a 'locked-off' phenotype [6].
• NarX contains a conserved 17 amino acid sequence, designated the 'P-box' element, that is essential for nitrate sensing [7].
• Diploid analysis of these narX mutants showed that a NarX P-box mutant which conferred a 'locked-on' phenotype was trans dominant over wild-type NarX [6].
• Based on patterns of target operon expression in various regulatory mutant strain backgrounds, most of the mutant NarX proteins appear to have alterations in negative control function [8].
• Here we show that mutations targeting a highly conserved sequence (the P box) in the periplasmic domain alter chemoreception by Nart and signaling by NarX similarly [9].

Anatomical context of ECs1727

• In this study, we have developed a sensitive anion-specific in vitro assay for NarX autophosphorylation by using Escherichia coli membranes highly enriched in the full-length NarX protein [10].

Associations of ECs1727 with chemical compounds

• Purified NarX was rapidly labeled when incubated with [gamma-32P] ATP but not with [alpha-32P]ATP in a reaction that required Mg2+ but was unaffected by nitrate [1].
• We also isolated single-residue substitutions in NarX that affect its ability to respond to or discriminate between nitrate and nitrite [4].
• NarX is a presumed sensor-transmitter for nitrate and possibly molybdenum detection [11].
• Nitrate regulation is mediated by the NarX-NarL two-component system, which activates the transcription of operons encoding nitrate respiration enzymes and represses the transcription of operons for other anaerobic respiratory enzymes, including enzymes involved in fumarate respiration [5].
• The conserved histidine and asparagine residues are essential for NarX and NarQ function, and this suggests that other two-component sensor-transmitter proteins may function in a similar fashion [12].

References