Either of two functionally redundant sensor proteins, NarX and NarQ, is sufficient for nitrate regulation in Escherichia coli K-12.
AUTOR(ES)
Rabin, R S
RESUMO
Nitrate acts through the response regulator NarL to activate and repress anaerobic respiratory gene expression in Escherichia coli. The narX gene product encodes a cognate sensor (histidine protein kinase). However, previous work discovered that NarL-mediated nitrate regulation is essentially normal in delta narX deletion mutants. In other two-component regulatory systems studied, the cognate sensor gene is essential for normal regulation. We suggested that NarX-mediated signal transduction reactions are also provided by a functionally redundant nitrate sensor, NarQ. We report here the identification and analysis of narQ insertion mutants. In narX+ strains, a narQ::Tn10 insertion had no perceptible effect on nitrate regulation. However, the same narQ::Tn10 insertion eliminated nitrate regulation when present in delta narX deletion strains. Thus, either narX+ or narQ+ was sufficient for essentially normal NarL-mediated nitrate regulation. The narQ gene mapped to 53 minutes on the E. coli genetic map, a location distinct from all known nitrate regulatory or target genes. The predicted NarQ sequence shares substantial similarity with NarX, particularly in the histidine protein kinase region and in a region of shared similarity with the methyl-accepting chemotaxis proteins. Both NarQ and NarX apparently have N-terminal periplasmic domains, but the primary structures of these regions are largely dissimilar in the two sequences. Analysis of narX* and narL missense alleles in narQ+ versus narQ::Tn10 backgrounds suggests that NarQ and NarX may have subtle functional differences.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=49931Documentos Relacionados
- The NarX and NarQ sensor-transmitter proteins of Escherichia coli each require two conserved histidines for nitrate-dependent signal transduction to NarL.
- Phosphorylation and dephosphorylation of the NarQ, NarX, and NarL proteins of the nitrate-dependent two-component regulatory system of Escherichia coli.
- Expression of the narX, narL, narP, and narQ genes of Escherichia coli K-12: regulation of the regulators.
- Nitrate regulation of anaerobic respiratory gene expression in narX deletion mutants of Escherichia coli K-12.
- Structure of genes narL and narX of the nar (nitrate reductase) locus in Escherichia coli K-12.