Transcriptional regulation of the macs1-fadD1 operon encoding two acyl-CoA synthases involved in the physiological differentiation of Streptomyces coelicolor

Abstract

The long-chain acyl-CoA synthase (ACS) FadD1 plays an important role in timing the levels of antibiotic production inStreptomyces coelicolor. fadD1andmacs1, encoding a putative medium-chain ACS, are part of a two-gene operon, whose expression is induced during the stationary phase of growth. Here it is reported that transcription of themacs1-fadD1operon is positively regulated by AcsR, a LuxR-type transcriptional regulator. In anacsRmutant, expression of themacs1-fadD1genes loses its normal up-regulation and the mutant becomes deficient in antibiotic production, in a clear correlation with the phenotype shown by afadD1null mutant. The absence ofmacs1-fadD1induction in theacsRmutant was restored by complementation with a wild-type copy of theacsRgene, showing a strict link between AcsR and induction of themacs1-fadD1operon. Gel mobility shift assays and DNase I footprinting indicated that AcsR binds to specific sequences about +162 nucleotides downstream of themacs1transcriptional start site. In the putative operator sequence three almost identical direct tandem repeats of seven nucleotides were identified where the central sequence is essential for AcsR recognition and binding. Transcriptional fusions of the divergent pacsRand pmacs1promoters indicated that AcsR does not regulate its own transcription, and that it binds to the operator region to control exclusively the growth-phase induction of themacs1-fadD1operon.