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Gene Review

prgX  -  negative regulator

Enterococcus faecalis

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Disease relevance of prgX

  • Here, we present the molecular structure of PrgX, a DNA- and peptide-binding protein that regulates expression of the conjugative transfer genes of the Enterococcus faecalis plasmid pCF10 in response to an intercellular peptide pheromone signal [1].

High impact information on prgX

  • Results confirmed the 5' end of a very abundant, constitutively produced transcript (from prgQ) that had been mapped previously by primer extension and defined the initiation point of a less abundant, divergently transcribed message (from prgX) [2].
  • Enterococcus faecalis pheromone-responsive protein PrgX: genetic separation of positive autoregulatory functions from those involved in negative regulation of conjugative plasmid transfer [3].
  • In this study, we isolated 14 single amino acid substitutions in PrgX that reduced or eliminated repression of prgQ, without affecting autoregulation or DNA binding [3].
  • However, both Qa RNA and PrgX protein were reduced in three Qa promoter region mutants and the expression of prgQ transcripts extending 3' from IRS1 became constitutive [4].
  • The pCF10-encoded negative regulators PrgX and Qa (prgQ antisense) RNA inhibit pCF10 transfer by blocking prgQ transcription extension past a potential transcription terminator sequence IRS1 [4].

Biological context of prgX

  • The results suggest that most of the amino acid sequence determinants of cCF10 pheromone activity affect interactions between the peptide and PrgX, although some sequence variants that affected peptide/PrgZ interactions were also identified [5].
  • To address these issues, we used a pheromone-inducible reporter gene system where various combinations of PrgX and PrgZ could be expressed in an isogenic host background to examine the biological activities of cCF10, iCF10, and variants of cCF10 isolated in a genetic screen [5].
  • Dominant-negative mutants of prgX: evidence for a role for PrgX dimerization in negative regulation of pheromone-inducible conjugation [6].
  • The primary binding site near prgX includes an 11 bp palindromic sequence and showed relatively high affinity for His-tagged PrgX (His-PrgX) [7].
  • A deletion spanning nucleotides+259 to +398 from the prgQ transcription initiation site abolished the prgX gene products at both RNA and protein levels [8].

Regulatory relationships of prgX

  • However, the relative importance of the interaction of these peptides with the pCF10 protein PrgZ (which enhances import of cCF10) versus PrgX is not fully understood, and there is relatively little information about specific amino acid sequence determinants affecting the functional interactions of cCF10 with these proteins in vivo [5].

Other interactions of prgX

  • The genes mapped include prgA (encoding Sec10) and prgB (encoding Asc10), as well as four putative regulatory genes, prgX, -R, -S, and -T [9].
  • The minimum segment required for negative control, as indentified by deletion analysis, was a 6.9-kb region extending from the 5' end of a gene called prgN, through a previously identified gene, prgX [10].

Analytical, diagnostic and therapeutic context of prgX

  • Although the size of the major Qa RNA detected by Northern blot analysis was too short (ca 120 nt) to be an mRNA for PrgX protein, the transcription from the Qa promoter was shown to proceed through to prgX [8].


  1. Structure of peptide sex pheromone receptor PrgX and PrgX/pheromone complexes and regulation of conjugation in Enterococcus faecalis. Shi, K., Brown, C.K., Gu, Z.Y., Kozlowicz, B.K., Dunny, G.M., Ohlendorf, D.H., Earhart, C.A. Proc. Natl. Acad. Sci. U.S.A. (2005) [Pubmed]
  2. Sensitive detection of bacterial transcription initiation sites and differentiation from RNA processing sites in the pheromone-induced plasmid transfer system of Enterococcus faecalis. Bensing, B.A., Meyer, B.J., Dunny, G.M. Proc. Natl. Acad. Sci. U.S.A. (1996) [Pubmed]
  3. Enterococcus faecalis pheromone-responsive protein PrgX: genetic separation of positive autoregulatory functions from those involved in negative regulation of conjugative plasmid transfer. Kozlowicz, B.K., Bae, T., Dunny, G.M. Mol. Microbiol. (2004) [Pubmed]
  4. Characterization of cis-acting prgQ mutants: evidence for two distinct repression mechanisms by Qa RNA and PrgX protein in pheromone-inducible enterococcal plasmid pCF10. Bae, T., Kozlowicz, B.K., Dunny, G.M. Mol. Microbiol. (2004) [Pubmed]
  5. Analysis of the Amino Acid Sequence Specificity Determinants of the Enterococcal cCF10 Sex Pheromone in Interactions with the Pheromone-Sensing Machinery. Fixen, K.R., Chandler, J.R., Le, T., Kozlowicz, B.K., Manias, D.A., Dunny, G.M. J. Bacteriol. (2007) [Pubmed]
  6. Dominant-negative mutants of prgX: evidence for a role for PrgX dimerization in negative regulation of pheromone-inducible conjugation. Bae, T., Dunny, G.M. Mol. Microbiol. (2001) [Pubmed]
  7. Two targets in pCF10 DNA for PrgX binding: their role in production of Qa and prgX mRNA and in regulation of pheromone-inducible conjugation. Bae, T., Kozlowicz, B., Dunny, G.M. J. Mol. Biol. (2002) [Pubmed]
  8. Analysis of expression of prgX, a key negative regulator of the transfer of the Enterococcus faecalis pheromone-inducible plasmid pCF10. Bae, T., Clerc-Bardin, S., Dunny, G.M. J. Mol. Biol. (2000) [Pubmed]
  9. Molecular and genetic analysis of a region of plasmid pCF10 containing positive control genes and structural genes encoding surface proteins involved in pheromone-inducible conjugation in Enterococcus faecalis. Kao, S.M., Olmsted, S.B., Viksnins, A.S., Gallo, J.C., Dunny, G.M. J. Bacteriol. (1991) [Pubmed]
  10. Identification and characterization of the genes of Enterococcus faecalis plasmid pCF10 involved in replication and in negative control of pheromone-inducible conjugation. Hedberg, P.J., Leonard, B.A., Ruhfel, R.E., Dunny, G.M. Plasmid (1996) [Pubmed]
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