Cloning and transcription analysis of the entire glycerol utilization (gylABX) operon of Streptomyces coelicolor A3(2) and identification of a closely associated transcription unit.

The entire glycerol utilization (gylABX) operon of Streptomyces coelicolor A3(2) was cloned and its transcriptional organization and regulation was analyzed by Northern blotting, S1 nuclease mapping and transcriptional fusions. Transcription of the operon is glycerol-inducible and glucose-repressible; glyA (presumptively encoding glycerol kinase), gylB (encoding sn-glycerol-3-phosphate dehydrogenase) and gylX (a non-essential 1.1 kb sequence) are transcribed consecutively to give a 5.4 kb mRNA. Two alternative transcription termination or gyl mRNA processing sites are located within the operon; one (a discrete site) lies between gylB and gylX and the other (a heterogeneous site) positioned 3 kb into the operon, may correspond to the gylA-gylB intercistronic region. A 0.9 kb glycerol-inducible transcription unit is located immediately upstream of gylABX. Transcriptional fusion studies employing an attP site-deleted phage vector provided complementary evidence for the organization of the operon.