Response to culture aeration mediated by the nitrate and nitrite sensor NarQ of Escherichia coli K-12.
Respiratory enzyme synthesis in enterobacteria is controlled in response to electron acceptor availability. The iron-sulphur protein Fnr and the sensor-regulator proteins ArcB-ArcA control respiratory gene transcription in response to oxygen and quinone pool redox status respectively. The sensor-regulator proteins NarX-NarL and NarQ-NarP control anaerobic respiratory gene expression in response to nitrate and nitrite. Our laboratory recently engineered the lac operon to replace the primary operator O1-lac with the NarL and NarP protein binding site from the nirB operon. Expression of the lacZ gene from this construct is repressed by nitrate in Nar+ strains. Here, we found that lacZ gene expression was repressed in aerated cultures of narQ+narX null strains. This repression was not observed in narX+narQ+ or narX+narQ null strains. Thus, the NarQ sensor responds to aeration as well as to nitrate and nitrite. The NarX and NarQ sensors are composed of three distinct modules: an amino-terminal sensory module, a carboxyl-terminal transmitter module and a central module of unknown function. Experiments with NarX-NarQ hybrid proteins suggest that the NarQ protein central module is necessary for response to aeration. The physiological significance of this additional sensory role for the NarQ sensor remains obscure.
Stewart
Valley
V
Section of Microbiology, University of California, One Shields Ave, Davis, CA 95616-8665, USA. vjstewart@ucdavis.edu
Chen
Li-Ling
LL
Wu
Hui-chung
HC
D001665:Binding Sites; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism*; D009876:Operon; D010084:Oxidation-Reduction; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D009566:Nitrates; D009573:Nitrites; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; C088708:narQ protein, E coli