Direct regulation of the ATPase activity of the transcriptional activator DmpR by aromatic compounds.

The NtrC-like regulator DmpR controls transcription from the dmp operon that encodes the enzymes for catabolism of phenol and some related aromatic compounds. DmpR activates transcription from the sigma 54-dependent dmp-operon promoter in the presence of pathway substrates or structural analogues in the growth medium. Using affinity-purified DmpR and a truncated derivative, we show here that aromatic compounds directly activate the ATPase activity of this protein in vitro, and that the amino-terminal domain represses this activity in the absence of an aromatic ligand. In order to dissect the activation process, derivatives of DmpR exhibiting single amino acid changes were isolated and their effector-dependence and specificity profiles were analysed in vivo. The mechanistic implications of the phenotypes of these mutants are discussed.