The Escherichia coli K-12 NarL and NarP proteins insulate the nrf promoter from the effects of integration host factor

Douglas F Browning*, David J Lee, Alan J Wolfe, Jeffrey A Cole, Stephen J W Busby

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The Escherichia coli K-12 nrf operon promoter can be activated fully by the FNR protein (regulator of fumarate and nitrate reduction) binding to a site centered at position -41.5. FNR-dependent transcription is suppressed by integration host factor (IHF) binding at position -54, and this suppression is counteracted by binding of the NarL or NarP response regulator at position -74.5. The E. coli acs gene is transcribed from a divergent promoter upstream from the nrf operon promoter. Transcription from the major acsP2 promoter is dependent on the cyclic AMP receptor protein and is modulated by IHF and Fis binding at multiple sites. We show that IHF binding to one of these sites, located at position -127 with respect to the nrf promoter, has a positive effect on nrf promoter activity. This activation is dependent on the face of the DNA helix, independent of IHF binding at other locations, and found only when NarL/NarP are not bound at position -74.5. Binding of NarL/NarP appears to insulate the nrf promoter from the effects of IHF. The acs-nrf regulatory region is conserved in other pathogenic E. coli strains and related enteric bacteria but differs in Salmonella enterica serovar Typhimurium.

Original languageEnglish
Pages (from-to)7449-7456
Number of pages8
JournalJournal of Bacteriology
Issue number21
Publication statusPublished - 1 Nov 2006


  • Artificial Gene Fusion
  • Base Sequence
  • Conserved Sequence/genetics
  • DNA, Bacterial/metabolism
  • DNA, Intergenic
  • DNA-Binding Proteins/physiology
  • Electrophoretic Mobility Shift Assay
  • Escherichia coli/physiology
  • Escherichia coli Proteins/metabolism
  • Gene Expression
  • Genes, Reporter
  • Integration Host Factors/metabolism
  • Iron-Sulfur Proteins/metabolism
  • Molecular Sequence Data
  • Promoter Regions, Genetic
  • Protein Binding
  • Salmonella typhimurium/genetics
  • beta-Galactosidase/analysis


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