Molecular and General Genetics MGG

, Volume 250, Issue 1, pp 50–58 | Cite as

Transcriptional regulation of the iron-responsive sigma factor genepbrA

  • Ray Sexton
  • Paul R. GillJr.
  • David N. Dowling
  • Fergal O'Gara
Original Paper


In response to the intracellular iron concentrationPseudomonas fluorescens M114 coordinately regulates the production of pseudobactin M114, its cognate receptor PbuA, and a casein protease. Transcriptional initiation of this coordinate iron-stress response requires the sigma factor PbrA. PbrA is a member of the ECF (Extracytoplasmicfunction) subgroup of the σ70 family of eubacterial RNA polymerase sigma factors. Regulatory studies of thepbrA gene utilising promoter-lacZ transcriptional fusions demonstrate that expression ofpbrA dictates the cellular response to iron.pbrA is transcribed in all phases of iron-limited growth but maximally at late-logarithmic to stationary phase.pbrA expression is independent of autoregulatory control but is strictly repressed in iron-rich conditions in a Fur-dependent fashion. Constitutive expression ofpbrA from an inducibletac promoter permits the induction of PbrA-dependent transcription and pseudobactin M114 biosynthesis in high-iron conditions. A PbrA consensus sequence was derived from significant DNA sequence homologies observed within the “ − 25 bp” and “ − 16 bp” regions conserved among all PbrA-dependent promoters. The predicted PbrA target promoter consensus is homologous for the promoter recognition sites for other environmentally responsive ECF sigma factors.

Key words

Iron regulation Sigma factor Fur Pseudomonas Siderophore 


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Copyright information

© Springer-Verlag 1996

Authors and Affiliations

  • Ray Sexton
    • 1
  • Paul R. GillJr.
    • 1
  • David N. Dowling
    • 1
  • Fergal O'Gara
    • 1
  1. 1.Microbiology DepartmentUniversity CollegeCorkIreland

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