RT Journal Article SR Electronic(1) A1 Palacios, Sergio A1 Escalante-Semerena, Jorge C.YR 2004 T1 2-Methylcitrate-dependent activation of the propionate catabolic operon (prpBCDE) of Salmonella enterica by the PrpR protein JF Microbiology, VO 150 IS 11 SP 3877 OP 3887 DO https://doi.org/10.1099/mic.0.27299-0 PB Microbiology Society, SN 1465-2080, AB 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 (PrpRc) with the highest 2-MC-independent activity. Residue A162 is critical to 2-MC sensing, since the mutant PrpR protein PrpRA162T was as active as the PrpRc 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 PprpBCDE promoter., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.27299-0