Evidence For Dissimilar Cyclic-Amp Receptor Protein Binding Sties In E. Coli LAC And ARA Promoter Regions
Recent work with a mutant CRP independent of the c-AMP requirement for induction of the lactose operon suggested that the CRP binding sites in the promoter regions of the inducible operons are dissimilar. A mutant strain was developed that is independent of the c-AMP requirement for induction of the arabinose operon, but dependent on c-AMP for induction of the lactose operon. While the mutation was not reliably mapped to crp, several lines of evidence indicate the genesis of a second form of c-AMP independent CRP selected for inducing ara. This suggests that CRP binding sites in lac and ara promoter regions are dissimilar, and therefore, all CRP binding sites are dissimilar. It is proposed that regulation of transcription may occur by unique variations in promoter region sequences.