title: Sigma 54 levels and physiological control of the Pseudomonas putida Pu promoter.
abstract: The cellular levels of the alternative sigma factor sigma(54) of Pseudomonas putida have been examined in a variety of growth stages and culture conditions with a single-chain Fv antibody tailored for detection of scarce proteins. The levels of sigma(54) were also monitored in P. putida strains with knockout mutations in ptsO or ptsN, known to be required for the C-source control of the sigma(54)-dependent Pu promoter of the TOL plasmid. Our results show that approximately 80 +/- 26 molecules of sigma(54) exist per cell. Unlike that in relatives of Pseudomonas (e.g., Caulobacter), where fluctuations of sigma(54) determine adaptation and differentiation when cells face starvation, sigma(54) in P. putida remains unexpectedly constant at different growth stages, in nitrogen starvation and C-source repression conditions, and in the ptsO and ptsN mutant strains analyzed. The number of sigma(54) molecules per cell in P. putida is barely above the predicted number of sigma(54)-dependent promoters. These figures impose a framework on the mechanism by which Pu (and other sigma(54)-dependent systems) may become amenable to physiological control.
authors.affiliation: Centro Nacional de Biotecnología del Consejo Superior de Investigaciones Científicas, Campus de Cantoblanco, 28049 Madrid, Spain.
authors.forename: Paola
authors.initials: P
authors.lastname: Jurado
authors.forename: Luis A
authors.initials: LA
authors.lastname: Fernández
authors.forename: Víctor
authors.initials: V
authors.lastname: de Lorenzo
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003470:Culture Media; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000235:genetics / Q000378:metabolism; D010957:Plasmids; D011401:Promoter Regions, Genetic; D016958:Pseudomonas putida / Q000254:growth & development* / Q000502:physiology; D051877:RNA Polymerase Sigma 54; D012808:Sigma Factor / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D004268:DNA-Binding Proteins; C423631:PtsN protein, Pseudomonas putida; D012808:Sigma Factor; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54