PhoP/PhoQ transcriptional repression of Salmonella typhimurium invasion genes: evidence for a role in protein secretion

Mol Microbiol. 1995 Jul;17(1):169-81. doi: 10.1111/j.1365-2958.1995.mmi_17010169.x.


Previously, the PhoP-repressed locus prgH was identified as important for signalling epithelial cells to endocytose Salmonella typhimurium. Characterization of prgH revealed that it is an operon of four genes encoding polypeptides of 392 (prgH), 80 (prgI), 101 (prgJ) and 252 amino acid residues (prgK). Synthesis of the 2.6 kb prgHIJK transcript was repressed in bacteria that activate PhoP/PhoQ, indicating that PhoP/PhoQ regulates prgHIJK by transcriptional repression. The prgI, prgJ and prgK predicted gene products were similar to Shigella flexneri and Yersinia enterocolitica proteins required for secretion of Ipa and Yop virulence factors. Analysis of the culture supernatants from wild-type S. typhimurium demonstrated that at least 25 polypeptides larger than 14 kDa could be detected. In contrast, prgH1::TnphoA, phoP-constitutive and hil-deletion mutants had significant defects in their supernatant protein profiles. The invasion and supernatant protein profile defects of the prgH1::TnphoA mutant were both complemented by a 5.1 kb plasmid that included prgHIJK. These results suggest that PhoP/PhoQ regulates extracellular transport of proteins by transcriptional repression of secretion determinants and that secreted proteins may be involved in signalling epithelial cells to endocytose bacteria.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Bacterial Proteins / physiology*
  • Base Sequence
  • Cloning, Molecular
  • Endocytosis / physiology
  • Epithelial Cells
  • Epithelium / microbiology
  • Gene Expression Regulation, Bacterial / physiology
  • Genes, Bacterial / genetics
  • Molecular Sequence Data
  • Operon / genetics
  • RNA, Bacterial / genetics
  • RNA, Messenger / genetics
  • Repressor Proteins / physiology*
  • Restriction Mapping
  • Salmonella typhimurium / genetics*
  • Salmonella typhimurium / pathogenicity
  • Sequence Analysis, DNA
  • Sequence Homology, Amino Acid
  • Transcription, Genetic / physiology


  • Bacterial Proteins
  • PhoQ protein, Bacteria
  • PrgH protein, Salmonella typhimurium
  • RNA, Bacterial
  • RNA, Messenger
  • Repressor Proteins
  • PhoP protein, Bacteria

Associated data

  • GENBANK/U21676