Location of essential sequence elements at the Escherichia coli melAB promoter.
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.
Keen
J
J
School of Biochemistry, University of Birmingham, U.K.
Williams
J
J
Busby
S
S
D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000378:metabolism; D015246:Deoxyribonuclease EcoRI; D015247:Deoxyribonuclease HindIII; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010957:Plasmids; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D015183:Restriction Mapping; D017384:Sequence Deletion; D015534:Trans-Activators / Q000378:metabolism; D001616:beta-Galactosidase / Q000096:biosynthesis
D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C077649:MelR protein, E coli; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D015246:Deoxyribonuclease EcoRI; D015247:Deoxyribonuclease HindIII; D001616:beta-Galactosidase