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Mol Gen Genet. 1998 May;258(4):442-7.

In vitro and in vivo characterization of three major dadAX promoters in Escherichia coli that are regulated by cyclic AMP-CRP and Lrp.

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Department of Biochemistry and Cell Biology, State University of New York at Stony Brook, 11794, USA.


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.

[Indexed for MEDLINE]

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