NtrC-dependent regulatory network for nitrogen assimilation in Pseudomonas putida.
Pseudomonas putida KT2440 is a model strain for studying bacterial biodegradation processes. However, very little is known about nitrogen regulation in this strain. Here, we show that the nitrogen regulatory NtrC proteins from P. putida and Escherichia coli are functionally equivalent and that substitutions leading to partially active forms of enterobacterial NtrC provoke the same phenotypes in P. putida NtrC. P. putida has only a single P(II)-like protein, encoded by glnK, whose expression is nitrogen regulated. Two contiguous NtrC binding sites located upstream of the sigma(N)-dependent glnK promoter have been identified by footprinting analysis. In vitro experiments with purified proteins demonstrated that glnK transcription was directly activated by NtrC and that open complex formation at this promoter required integration host factor. Transcription of genes orthologous to enterobacterial codB, dppA, and ureD genes, whose transcription is dependent on sigma(70) and which are activated by Nac in E. coli, has also been analyzed for P. putida. Whereas dppA does not appear to be regulated by nitrogen via NtrC, the codB and ureD genes have sigma(N)-dependent promoters and their nitrogen regulation was exerted directly by NtrC, thus avoiding the need for Nac, which is missing in this bacterial species. Based upon these results, we propose a simplified nitrogen regulatory network in P. putida (compared to that in enterobacteria), which involves an indirect-feedback autoregulation of glnK using NtrC as an intermediary.
Hervás
Ana B
AB
Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide/CSIC, Seville, Spain.
Canosa
Inés
I
Little
Richard
R
Dixon
Ray
R
Santero
Eduardo
E
D000483:Alleles; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D001665:Binding Sites / Q000235:genetics; D018983:DNA Footprinting; D029968:Escherichia coli Proteins / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics; D009584:Nitrogen / Q000378:metabolism*; D051922:PII Nitrogen Regulatory Proteins / Q000235:genetics / Q000502:physiology; D033902:Periplasmic Binding Proteins / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D016958:Pseudomonas putida / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D051922:PII Nitrogen Regulatory Proteins; D033902:Periplasmic Binding Proteins; D014157:Transcription Factors; C086767:UreD protein, Bacteria; C497876:glnG protein, E coli; C066768:dppA protein, E coli; C075818:codB protein, E coli; D009584:Nitrogen