PHENOBARBITAL AND SULFONYLUREA-INDUCIBLE OPERONS ENCODING HERBICIDE METABOLIZING CYTOCHROMES-P-450 IN STREPTOMYCES-GRISEOLUS

We have identified the promoters for two inducible genes, in Streptomy ces griseolus, that encode herbicide-metabolizing cytochromes P-450. T hey are in the class of promoters that have -35 and -10 sequences simi lar to those used in Escherichia coli by RNA polymerase E-sigma-70. Tr anscription from either promoter was shown to be induced by sulfonylur ea (chlorimuron ethyl) or phenobarbital. Mapping of mRNA showed that e ach cytochrome P450-encoding gene was transcribed on a separate multic istronic mRNA that encodes cytochrome P-450 (suaC or subC), ferredoxin (suaB or subB) and at least one other open reading frame. An inducibl e, site-specific DNA-binding activity was identified that bound to two similar 8-bp inverted repeat sequences within or near the sua promote r (suaP). A noninducible DNA-binding activity, distinct from that whic h bound to suaP, was found that bound to an 11-bp inverted repeat at t he sub transcription start point.