In Vitro Analysis of the Butyrolactone Autoregulator Receptor Protein (FarA) of Streptomyces lavendulae FRI-5 Reveals that FarA Acts as a DNA-Binding Transcriptional Regulator That Controls Its Own Synthesis

FarA of Streptomyces lavendulae FRI-5 is a specific receptor protein for IM-2, a butyrolactone autoregulator that controls the production of a blue pigment and the nucleoside antibiotics showdomycin and minimycin. Gel shift assays demonstrated that FarA binds to the farA upstream region and that this binding is abolished in the presence of IM-2. The FarA binding sequence was localized by DNase I footprinting to a 28-bp sequence located approximately 70 bp upstream of the farA translational start site. High-resolution S1 nuclease mapping of farA transcripts revealed a putative transcription start site, located at an A residue positioned 64 bp upstream from the farA translation start codon and 4 bp downstream from an Escherichia coli ς(70)-like −10 recognition region. The FarA-binding sequence overlaps this −10 region and contains the farA transcription initiation site, suggesting that FarA acts as a repressor that, in the absence of IM-2, represses transcription of farA.