Differential DNA bending introduced by the XXXX LysR-type regulator, CatR, at the plasmid-borne pheBA and chromosomal catBC promoters.

@entity15250 @entity3457 @entity3971 @entity22761 @entity3337 @entity6153
The plasmid-borne pheBA operon of @entity15250 PaW85 allows growth of the host cells on @entity3971 . The promoter of this operon is activated by the chromosomally encoded LysR-type regulator CatR, in the presence of the inducer @entity22761 . @entity22761 is an intermediate of @entity6153 degradation by the chromosomally encoded ortho or beta-ketoadipate pathway. The catBC operon encodes two enzymes of the beta-ketoadipate pathway and also requires CatR and @entity22761 for its expression. The promoters of the pheBA and catBC operons are highly homologous, and since both respond to CatR, it is likely that the pheBA promoter was recruited from the ancestral catBC promoter. Gel shift assays and DNase I footprinting have shown that the pheBA promoter has a higher binding affinity for CatR than the catBC promoter. Like the catBC promoter, the pheBA promoter forms two complexes (C1 and C2) with CatR in the absence of @entity22761 , but only forms a single complex (C2) in the presence of @entity22761 . Like the catBC promoter CatR @entity3337 ( @entity3337 ) and @entity3457 ( @entity3457 ) arrangement, the pheBA promoter demonstrates the presence of a 26 bp segment highly homologous to the @entity3337 that is protected by CatR from DNase I digestion in the absence of the inducer. An additional 16 bp sequence, similar to the catBC promoter @entity3457 , is protected only when the inducer @entity22761 is present. The binding of CatR in absence of @entity22761 bends the catBC and pheBA promoter regions to significantly different degrees, but CatR binding in the presence of @entity22761 results in a similar degree of DNA bending. The evolutionary implications of the interactions of CatR with these two promoters are discussed.
