title: 2-Methylcitrate-dependent activation of the propionate catabolic operon (prpBCDE) of Salmonella enterica by the PrpR protein.
abstract: The function of the PrpR protein of Salmonella enterica serovar Typhimurium LT2 was studied in vitro and in vivo. The PrpR protein is a sensor of 2-methylcitrate (2-MC), an intermediate of the 2-methylcitric acid cycle used by this bacterium to convert propionate to pyruvate. PrpR was unresponsive to citrate (a close structural analogue of 2-MC) and to propionate, suggesting that 2-MC, not propionate, is the metabolite that signals the presence of propionate in the environment to S. enterica. prpR alleles encoding mutant proteins with various levels of 2-MC-independent activity were isolated. All lesions causing constitutive PrpR activity were mapped to the N-terminal domain of the protein. Removal of the entire sensing domain resulted in a protein (PrpR(c)) with the highest 2-MC-independent activity. Residue A162 is critical to 2-MC sensing, since the mutant PrpR protein PrpR(A162T) was as active as the PrpR(c) protein in the absence of 2-MC. DNA footprinting studies identified the site in the region between prpR and the prpBCDE operon to which the PrpR protein binds. Analysis of the binding-site sequence revealed two sites with dyad symmetry. Results from DNase I footprinting assays suggested that the PrpR protein may have higher affinity for the site proximal to the P(prpBCDE) promoter.
authors.affiliation: Department of Bacteriology, University of Wisconsin, 1710 University Avenue, Madison, WI 53726-4087, USA.
authors.forename: Sergio
authors.initials: S
authors.lastname: Palacios
authors.affiliation: Department of Bacteriology, University of Wisconsin, 1710 University Avenue, Madison, WI 53726-4087, USA.
authors.forename: Jorge C
authors.initials: JC
authors.lastname: Escalante-Semerena
mesh_terms: D000222:Adaptation, Physiological; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D002951:Citrates / Q000378:metabolism* / Q000494:pharmacology; D018983:DNA Footprinting; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D020536:Enzyme Activators / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation; D009876:Operon; D011401:Promoter Regions, Genetic; D011422:Propionates / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012486:Salmonella typhimurium / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D002951:Citrates; D004268:DNA-Binding Proteins; D020536:Enzyme Activators; D011422:Propionates; C031605:2-methylcitric acid; D000251:Adenosine Triphosphatases