2-Methylcitrate-dependent activation of the propionate catabolic operon (prpBCDE) of Salmonella enterica by the PrpR protein

Microbiology (Reading). 2004 Nov;150(Pt 11):3877-3887. doi: 10.1099/mic.0.27299-0.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adaptation, Physiological
  • Adenosine Triphosphatases / genetics
  • Adenosine Triphosphatases / metabolism
  • Bacterial Proteins / genetics
  • Bacterial Proteins / physiology*
  • Citrates / metabolism*
  • Citrates / pharmacology
  • DNA Footprinting
  • DNA Mutational Analysis
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / physiology*
  • Enzyme Activators / pharmacology
  • Gene Expression Regulation, Bacterial*
  • Mutation
  • Operon*
  • Promoter Regions, Genetic
  • Propionates / metabolism*
  • Protein Binding
  • Protein Structure, Tertiary
  • Salmonella typhimurium / genetics*
  • Salmonella typhimurium / metabolism
  • Signal Transduction / physiology


  • Bacterial Proteins
  • Citrates
  • DNA-Binding Proteins
  • Enzyme Activators
  • Propionates
  • 2-methylcitric acid
  • Adenosine Triphosphatases