Participation of the purine repressor in control of the carbamoylphosphate synthetase operon in Salmonella typhimurium

Molecular Microbiology
C D LuA T Abdelal

Abstract

Previous work has shown that the carAB operon of Salmonella typhimurium is transcribed from tandem promoters, P1 and P2, that are negatively controlled by pyrimidines and arginine, respectively. The results reported here show that purines also negatively control expression of carAB and that this effect is absent in a purR::Tn10 derivative. Primer-extension experiments established that the purine effect is exerted at P1, thus redefining this promoter as sensitive to both purines and pyrimidines. The results of gel-retardation experiments as well as DNase I and premethylation footprintings indicate that the purine repressor interacts with a PUR box 85 bp upstream of P1. Modification of this PUR box by site-directed mutagenesis abolishes the repression by purines in a carA::lacZ fusion, confirming that this box functions in vivo in purine control of carAB expression.

Citations

Jun 7, 2008·Microbiology and Molecular Biology Reviews : MMBR·Charles L Turnbough, Robert L Switzer
Oct 3, 2001·Journal of Molecular Biology·D SzwajkajzerJ Carey
Dec 1, 2004·EcoSal Plus·Daniel Charlier, Nicolas Glansdorff

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