In the presence of 2-hydroxybiphenyl, the enhancer binding protein, HbpR, activates ther54-dependent PhbpC promoter and controls the initial steps of 2-hydroxybiphenyl degradation inPseudomonas azelaica. In the activa-tion process, an oligomeric HbpR complex of unknown subunit composi-tion binds to an operator region containing two imperfect palindromic sequences. Here, the HbpR–DNA binding interactions were investigated by site-directed mutagenesis of the operator region and by DNA-binding assays using purified HbpR. .
