Participation of the purine repressor in control of the carbamoylphosphate synthetase operon in Salmonella typhimurium.
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.
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Biology Department, Georgia State University, Atlanta 30303, USA.
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D000595:Amino Acid Sequence; D001120:Arginine / Q000494:pharmacology; D001483:Base Sequence; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing) / Q000096:biosynthesis* / Q000235:genetics; D017931:DNA Primers; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D019271:Hypoxanthine; D007042:Hypoxanthines / Q000494:pharmacology; D008969:Molecular Sequence Data; D009876:Operon; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D011687:Purines / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology; D012486:Salmonella typhimurium / Q000201:enzymology / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid
D017931:DNA Primers; D007042:Hypoxanthines; D011687:Purines; D011743:Pyrimidines; D019271:Hypoxanthine; D001120:Arginine; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing)