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. 1996 Sep 1;318(Pt 2):443–449. doi: 10.1042/bj3180443

Location of essential sequence elements at the Escherichia coli melAB promoter.

J Keen 1, J Williams 1, S Busby 1
PMCID: PMC1217641  PMID: 8809031

Abstract

The Escherichia coli melAB promoter has been cloned on a short DNA fragment and subjected to deletion mutagenesis, random mutagenesis and site-directed mutagenesis. In previous work we had shown that expression from the melAB promoter is triggered by melibiose and that this requires the MelR transcription activator. Melibiose-dependent expression is suppressed by deletions that remove both DNA-binding sites for MelR and by point mutations in the -10 hexamer, the -35 hexamer and the region just upstream of the -35 hexamer. The point mutations identify promoter elements that are essential for triggering the melAB promoter. The importance of these elements was confirmed by site-directed mutagenesis. The results show that the organization of the melAB promoter is fundamentally different from the organization of other bacterial promoters controlled by homologues of MelR.

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Selected References

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