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J Bacteriol. 2012 Jan;194(2):406-12. doi: 10.1128/JB.06353-11. Epub 2011 Nov 11.

Involvement of the global Crp regulator in cyclic AMP-dependent utilization of aromatic amino acids by Pseudomonas putida.

Author information

1
Consejo Superior de Investigaciones Científicas, Estación Experimental del Zaidín, Department of Environmental Protection, Granada, Spain.

Abstract

The phhAB operon encodes a phenylalanine hydroxylase involved in the conversion of L-phenylalanine into L-tyrosine in Pseudomonas putida. The phhAB promoter is transcribed by RNA polymerase sigma-70 and is unusual in that the specific regulator PhhR acts as an enhancer protein that binds to two distant upstream sites (-75 to -92 and -132 to -149). There is an integration host factor (IHF) binding site that overlaps the proximal PhhR box, and, consequently, IHF acts as an inhibitor of transcription. Use of L-phenylalanine is compromised in a crp-deficient background due to reduced expression from the phhAB promoter. Electrophoretic mobility shift assays and DNase I footprinting assays reveal that Crp binds at a site centered at -109 only in the presence of cyclic AMP (cAMP). We show, using circular permutation analysis, that the simultaneous binding of Crp/cAMP and PhhR bends DNA to bring positive regulators and RNA polymerase into close proximity. This nucleoprotein complex promotes transcription from phhA only in response to L-phenylalanine.

PMID:
22081386
PMCID:
PMC3256677
DOI:
10.1128/JB.06353-11
[Indexed for MEDLINE]
Free PMC Article

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