Studies on the roles of GlnK an GlnB in regulating Klebsiella pneumoniae NifL-dependent nitrogen control

• Published in: FEMS microbiology letters Vol. 180; no. 2; pp. 263 - 270
• Main Authors: Arcondeguy, T, Heeswijk, W.C. van, Merrick, M
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 15-11-1999; Blackwell; Oxford University Press
• Subjects: Bacterial Proteins - drug effects; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Biological and medical sciences; Blotting, Western; Carrier Proteins - genetics; Carrier Proteins - metabolism; E coli; Escherichia coli; Escherichia coli - genetics; Escherichia coli - metabolism; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation, Bacterial; Genes, Bacterial; genetic regulation; Genetics; glnB; glnK; Intracellular; Klebsiella; Klebsiella pneumoniae; Klebsiella pneumoniae - genetics; Klebsiella pneumoniae - metabolism; Microbiology; Modulation; Nitrogen; Nitrogen - metabolism; Nitrogen fixation; Nitrogen Fixation - genetics; Nitrogen regulation; Nitrogenation; PII Nitrogen Regulatory Proteins; Proteins; Signal transduction; signal transduction proteins; Substitutes; Transcription; Transcription Factors - drug effects; Transcription Factors - metabolism; Transcription, Genetic; Nitrogen regulation; Nitrogen fixation; Plasmid; Signal transduction; Genome organization; Heterologous system; Escherichia coli; Bacteria; Gene expression; In vitro; Klebsiella pneumoniae; Protein; Enterobacteriaceae
• ISSN: 0378-1097; 1574-6968
• DOI: 10.1111/j.1574-6968.1999.tb08805.x

In Klebsiella pnuemoniae, nitrogen fixation (nif) genes are regulated in response to fixed nitrogen and oxygen. The activity of the nif-specific transcriptional activator NifA is modulated by NifL, which mediates both oxygen and nitrogen control. The signal transduction protein GlnK is required to relieve the inhibitory effect of NifL on NifA that occurs when the intracellular N status is high and in a wild-type cell, the action of GlnK cannot be substituted by the structurally related protein PII. We have studied the modulation of NifA activity by NifL in an heterologous system in which the host organism is Escherichia coli. Using a deltaglnB,deltaglnK mutant, we show that the modulation of NifA activity by NifL is dependent on the concentration of GlnK in the cell and that when overproduced, PII can substitute from Glnk. Furthermore, our data suggest that PII can counteract the positive action of GlnK in relieving NifL-dependent inhibition of NifA activity. This negative effect of PII may be physiologically important in establishing repression of nif gene expression when the intracellular nitrogen status rises.