DIRECT REGULATION OF THE ATPASE ACTIVITY OF THE TRANSCRIPTIONAL ACTIVATOR DMPR BY AROMATIC-COMPOUNDS

The NtrC-like regulator DmpR controls transcription from the dmp opero n that encodes the enzymes for catabolism of phenol and some related a romatic compounds. DmpR activates transcription from the sigma(54)- de pendent dmp-operon promoter in the presence of pathway substrates or s tructural analogues in the growth medium. Using affinity-purified DmpR and a truncated derivative, we show here that aromatic compounds dire ctly activate the ATPase activity of this protein in vitro, and that t he amino-terminal domain represses this activity in the absence of an aromatic ligand. In order to dissect the activation process, derivativ es of DmpR exhibiting single amino acid changes were isolated and thei r effector-dependence and specificity profiles were analysed in vivo. The mechanistic implications of the phenotypes of these mutants are di scussed.