Phenobarbital and sulfonylurea-inducible operons encoding herbicide metabolizing cytochromes P-450 in Streptomyces griseolus.

We have identified the promoters for two inducible genes, in Streptomyces griseolus, that encode herbicide-metabolizing cytochromes P-450. They are in the class of promoters that have -35 and -10 sequences similar to those used in Escherichia coli by RNA polymerase E sigma 70. Transcription from either promoter was shown to be induced by sulfonylurea (chlorimuron ethyl) or phenobarbital. Mapping of mRNA showed that each cytochrome P450-encoding gene was transcribed on a separate multicistronic mRNA that encodes cytochrome P-450 (suaC or subC), ferredoxin (suaB or subB) and at least one other open reading frame. An inducible, site-specific DNA-binding activity was identified that bound to two similar 8-bp inverted repeat sequences within or near the sua promoter (suaP). A noninducible DNA-binding activity, distinct from that which bound to suaP, was found that bound to an 11-bp inverted repeat at the sub transcription start point.