PMID:9648752

Citation	Zhi, J, Mathew, E and Freundlich, M (1998) In vitro and in vivo characterization of three major dadAX promoters in Escherichia coli that are regulated by cyclic AMP-CRP and Lrp. Mol. Gen. Genet. 258:442-7
Abstract	We have shown previously that the dadAX operon of Escherichia coli expresses multiple transcripts, which are repressed by leucine-responsive regulatory protein (Lrp). Here we used site-directed mutagenesis and in vitro and in vivo transcription assays to show that each of the three major dad transcripts requires a specific promoter. These promoters, P1-P3, overlap and are positively regulated in vivo by cyclic AMP-CRP. DNase I footprinting experiments localized two CRP binding sites in this region: CRP1, which is positioned upstream of P1-P3, and CRP2, which is located within the promoters. Site-directed mutagenesis of each site provided evidence that CRP1 is necessary for the effects of cyclic AMP-CRP on dad expression in vivo and in vitro, and that CRP2 probably plays little or no role in this process.
Links	PubMed
Keywords	Alanine Racemase/genetics; Bacterial Proteins/physiology; Base Sequence; Binding Sites/genetics; Carrier Proteins; Cyclic AMP Receptor Protein/physiology; D-Amino-Acid Oxidase/genetics; DNA Footprinting; DNA, Bacterial/chemistry; DNA, Bacterial/metabolism; DNA-Binding Proteins/physiology; Escherichia coli/enzymology; Escherichia coli/genetics; Escherichia coli Proteins; Leucine-Responsive Regulatory Protein; Molecular Sequence Data; Mutagenesis, Site-Directed; Promoter Regions, Genetic; Transcription Factors; Transcription, Genetic
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