title: Genes for carbon metabolism and the ToxA virulence factor in Pseudomonas aeruginosa are regulated through molecular interactions of PtxR and PtxS.
abstract: Homologs of the transcriptional regulator PtxS are omnipresent in Pseudomonas, whereas PtxR homologues are exclusively found in human pathogenic Pseudomonas species. In all Pseudomonas sp., PtxS with 2-ketogluconate is the regulator of the gluconate degradation pathway and controls expression from its own promoter and also from the P(gad) and P(kgu) for the catabolic operons. There is evidence that PtxS and PtxR play a central role in the regulation of exotoxin A expression, a relevant primary virulence factor of Pseudomonas aeruginosa. We show using DNaseI-footprint analysis that in P. aeruginosa PtxR binds to the -35 region of the P(toxA) promoter in front of the exotoxin A gene, whereas PtxS does not bind to this promoter. Bioinformatic and DNaseI-footprint analysis identified a PtxR binding site in the P(kgu) and P(gad) promoters that overlaps the -35 region, while the PtxS operator site is located 50 bp downstream from the PtxR site. In vitro, PtxS recognises PtxR with nanomolar affinity, but this interaction does not occur in the presence of 2-ketogluconate, the specific effector of PtxS. DNAaseI footprint assays of P(kgu) and P(gad) promoters with PtxS and PtxR showed a strong region of hyper-reactivity between both regulator binding sites, indicative of DNA distortion when both proteins are bound; however in the presence of 2-ketogluconate no protection was observed. We conclude that PtxS modulates PtxR activity in response to 2-ketogluconate by complex formation in solution in the case of the P(toxA) promoter, or via the formation of a DNA loop as in the regulation of gluconate catabolic genes. Data suggest two different mechanisms of control exerted by the same regulator.
authors: Department of Environmental Protection, CSIC-EEZ, Granada, Spain.
authors: Abdelali
authors: A
authors: Daddaoua
authors: Sandy
authors: S
authors: Fillet
authors: Matilde
authors: M
authors: Fernández
authors: Zulema
authors: Z
authors: Udaondo
authors: Tino
authors: T
authors: Krell
authors: Juan L
authors: JL
authors: Ramos
mesh_terms: D036002:ADP Ribose Transferases / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002244:Carbon / Q000378:metabolism*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005098:Exotoxins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics*; D005942:Gluconates / Q000378:metabolism; D009876:Operon / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000378:metabolism*; D012996:Solutions; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D002244:Carbon; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D005098:Exotoxins; D005942:Gluconates; D012996:Solutions; D014157:Transcription Factors; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A; C113064:PtxS protein, Pseudomonas aeruginosa; C073470:LysR protein, Bacteria; C030691:gluconic acid