Transcriptional control of the iron-responsive fxbA gene by the mycobacterial regulator IdeR

Olivier Dussurget, Juliano Timm, Manuel Gomez, Benjamin Gold, Shengwei Yu, Sue Z. Sabol, Randall K. Holmes, William R. Jacobs, Issar Smith

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Abstract

Exochelin is the primary extracellular siderophore of Mycobacterium smegmatis, and the iron-regulated fxbA gene encodes a putative formyltransferase, an essential enzyme in the exochelin biosynthetic pathway (E. H. Fiss, Y. Yu, and W. R. Jacobs, Jr., Mol. Microbiol. 14:557-569, 1994). We investigated the regulation of fxbA by the mycobacterial IdeR, a homolog of the Corynebacterium diphtheriae iron regulator DtxR (M.P. Schmitt, M. Predich, L. Doukhan, I. Smith, and R. K. Holmes, Infect. Immun. 63:4284- 4289, 1995). Gel mobility shift experiments showed that IdeR binds to the fxbA regulatory region in the presence of divalent metals. DNase I footprinting assays indicated that IdeR binding protects a 28-bp region containing a palindromic sequence of the fxbA promoter that was identified in primer extension assays, fxbA regulation was measured in M. smegmatis wild- type and ideR mutant strains containing fxbA promoter-lacZ fusions. These experiments confirmed that fxbA expression is negatively regulated by iron and showed that inactivation of ideR results in iron-independent expression of fxbA. However, the levels of its expression in the ideR mutant were approximately 50% lower than those in the wild-type strain under iron limitation, indicating an undefined positive role of IdeR in the regulation of fxbA.

Original languageEnglish (US)
Pages (from-to)3402-3408
Number of pages7
JournalJournal of Bacteriology
Volume181
Issue number11
Publication statusPublished - Jun 1 1999

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ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

Cite this

Dussurget, O., Timm, J., Gomez, M., Gold, B., Yu, S., Sabol, S. Z., ... Smith, I. (1999). Transcriptional control of the iron-responsive fxbA gene by the mycobacterial regulator IdeR. Journal of Bacteriology, 181(11), 3402-3408.