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Cytosolic intermediates for cell wall biosynthesis and degradation control inducible beta-lactam resistance in

C Jacobs1, J M Frère, S Normark

  • 1Centre d'Ingénierie des Protéines, Université de Liège, Belgium.

Cell
|March 21, 1997
PubMed

Insights

Gram-negative bacteria control beta-lactamase production using AmpR and muropeptides. Muropeptides act antagonistically, with UDP-MurNAc-pentapeptide inhibiting and anhMurNAc-tripeptide restoring AmpR activation of beta-lactamase synthesis.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • Beta-lactamase induction in gram-negative bacteria is crucial for antibiotic resistance.
  • This process requires the transcriptional regulator AmpR and cytoplasmic muropeptides.

Purpose of the Study:

  • To elucidate the regulatory mechanism of beta-lactamase (ampC) gene expression.
  • To investigate the role of muropeptides in controlling AmpR-mediated transcriptional activation.

Main Methods:

  • In vitro transcription assays using purified AmpR.
  • Analysis of AmpR mutants (e.g., AmpR(G102E)) for constitutive ampC activation.
  • Testing the effects of specific muropeptides (UDP-MurNAc-pentapeptide, anhMurNAc-tripeptide) on AmpR activity.

Main Results:

  • Purified AmpR activates ampC beta-lactamase synthesis in vitro.
  • UDP-MurNAc-pentapeptide inhibits AmpR-mediated activation, but not in a constitutive AmpR mutant.
  • anhMurNAc-tripeptide counteracts UDP-MurNAc-pentapeptide's inhibition, restoring AmpR's inductive capacity.

Conclusions:

  • Cytosolic murein intermediates act antagonistically to regulate beta-lactamase expression.
  • This system functions as a cell-wall sensing mechanism controlling antibiotic resistance.
  • Understanding this pathway offers potential targets for novel antimicrobial strategies.

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