f The Homologous Regulators ANR of Pseudomonas Aeruginosa and FNR of Escherichia Coli have Overlapping but Distinct Specificities for Anaerobically Inducible Promoters
- Authors: Harald V. Winteler, Dieter Haas*M
- *Author for correspondence: Dieter Haas. Tel: +41 21 692 56 31. Fax: +41 21 692 56 35.
- First Published Online: 01 March 1996, Microbiology 142: 685-693, doi: 10.1099/13500872-142-3-685
- Subject: Genetics And Molecular Biology
- Issue Published:
The anaerobic transcriptional regulator ANR induces the arginine deiminase and denitrification pathways in Pseudomonas aeruginosa during oxygen limitation. The homologous activator FNR of Escherichia coli when introduced into an anr mutant of P. aeruginosa could functionally replace ANR for anaerobic growth on nitrate but not for anaerobic induction of arginine deiminase. In an FNR-positive E. coli strain, the ANR-dependent promoter of the arcDABC operon, which encodes the enzymes of the arginine deiminase pathway, was not expressed. To analyse systematically these distinct induction patterns, a lacZ promoter-probe, broad-host-range plasmid containing various −40 regions (the ANR/FNR recognition sequences) and −10 promoter sequences was constructed. These constructs were tested in P. aeruginosa and in E. coli expressing either ANR or FNR. In conjunction with the consensus −10 hexamer of E. coli σ70 RNA polymerase (TATAAT), the consensus FNR site (TTGAT….ATCAA) was recognized efficiently by ANR and FNR in both hosts. By contrast, when promoters contained the Arc box (TTGAC…. ATCAG), which is found in the arcDABC promoter, or a symmetrical mutant FNR site (CTGAT…. ATCAG), ANR was a more effective activator than was FNR. Conversely, an extended 22 bp, fully symmetrical FNR site allowed better activation with FNR than with ANR. Combination of the arc promoter −10 sequence (CCTAAT) with the Arc box or the consensus FNR site resulted in good ANR-dependent expression in P. aeruginosa but gave practically no expression in E. coli suggesting that RNA polymerase of P. aeruginosa differs from the E. coli enzyme in −10 recognition specificity. In conclusion, ANR and FNR are able to activate the RNA polymerases of P. aeruginosa and E. coli when the −40 and −10 promoter elements are identical or close to the E. coli consensus sequences.
© Society for General Microbiology 1996 | Published by the Microbiology Society
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