Regulation of microcin C51 operon expression: The role of global regulators of transcription

Dmitrii Fomenko, Alexandr Veselovskii, Inessa Khmel

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


Expression of the microcin C51 operon in Escherichia coli cells is regulated as a function of the phase of growth; it is stimulated during the decelerating phase of growth. Using single-copy Pmcc-lac transcriptional fusion (the promoter region of the microcin C51 operon fused to a promoterless lac operon in λ phage), we showed that transcription from the microcin operon promoter is dependent on σs (RpoS) factor. However, some level of Pmcc-lac expression is possible in rpoS null mutants, indicating that another sigma factor might be involved in transcription of the microcin C51 operon. Overproduction of σ70 decreased Pmcc-directed transcription, presumably as a result of competition of sigma factors for the limited amount of core RNA polymerase. The cyclic AMP-CRP complex was shown to stimulate transcription from Pmcc: the absence of CRP or cAMP in crp or cya mutant cells strongly decreased the level of Pmcc-lac expression. The production of C51 microcin decreased or was absent in rpoS, crp and cya mutant cells. Leucine-responsive protein Lrp and histone-like protein H-NS repressed Pmcc-lac expression in the exponential and decelerating phases of growth. In studies of Pmcc-lac expression in double mutant cells, we showed that proteins CRP, Lrp and H-NS acted in rpoS-dependent and rpoS-independent ways in transcription of the microcin C51 operon. Mutation hns- resulted in an increase in Pmcc-lac expression in crp, rpoS and lrp mutant cells, as in wild-type cells.

Original languageEnglish (US)
Pages (from-to)469-479
Number of pages11
JournalResearch in Microbiology
Issue number5
StatePublished - 2001
Externally publishedYes


  • CRP
  • Global regulators of transcription
  • H-NS
  • Lrp
  • Microcin C51 operon
  • Promoter
  • Sigma S factor
  • Stationary phase

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

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