SENSING OF AROMATIC-COMPOUNDS BY THE DMPR TRANSCRIPTIONAL ACTIVATOR OF PHENOL-CATABOLIZING PSEUDOMONAS SP STRAIN CF600

The dmp operon of the pVI150 catabolic plasmid of Pseudomonas sp. stra in CF600 encodes the enzymes involved in the catabolism of phenol and methylphenols. The regulator of this dmp pathway, DmpR, is a member of the NtrC family of transcriptional activators and controls transcript ion of the dmp operon in response to aromatic effector compounds (V. S hingler, M. Bartilson, and T. Moore, J. Bacteriol. 175:1596-1604, 1993 ). Using a lux gene fusion reporter system, in which the DmpR-regulate d operon promoter controls the expression of luciferase activity, we h ave shown in the study reported here that DmpR is activated by, but re sponds differentially to, the presence of a wide range of aromatic com pounds. In many microbial regulatory systems, including some members o f the NtrC family, the response to environmental fluctuations involves information transfer from surface sensory proteins to transcriptional regulators. However, DmpR-mediated activation of phenol metabolism in response to aromatic compounds occurs in the absence of a specific se nsory protein. We used hybrids between DmpR and XylR, a structurally r elated regulator of toluene and xylene metabolism, to demonstrate that it is the amino-terminal domains of these regulators that determine t he specificity of transcriptional activation. The results suggest that it is the direct interaction of aromatic compounds with the DmpR and XylR proteins that regulates their transcriptional promoting activity.