title: Characterization of the expression of the thcB gene, coding for a pesticide-degrading cytochrome P-450 in Rhodococcus strains.
abstract: A cytochrome P-450 system in Rhodococcus strains, encoded by thcB, thcC, and thcD, participates in the degradation of thiocarbamates and several other pesticides. The regulation of the system was investigated by fusing a truncated lacZ in frame to thcB, the structural gene for the cytochrome P-450 monooxygenase. Analysis of the thcB-lacZ fusion showed that the expression of thcB was 10-fold higher in the presence of the herbicide EPTC (s-ethyl dipropylthiocarbamate). Similar enhancement of the thcB-lacZ expression was found with other thiocarbamate pesticides. Atrazine, simazine, or carbofuran, although metabolized by the system, had no effect on the thcB-lacZ expression. The presence of glucose slightly increased the expression of thcB-lacZ, indicating no catabolic repression of the thcB-lacZ expression. The expression of thcB-lacZ was decreased more than twofold in Luria-Bertani medium. This was due in part to cysteine, which repressed thcB-lacZ expression. It was confirmed that the thcR gene, which is transcribed divergently from thcB, codes for a positive regulatory protein which is essential for the thcB-lacZ expression. Studies of the thcR-lacZ protein fusion showed that the thcR gene is expressed constitutively.
authors.affiliation: Centre for Land and Biological Resources Research, Agriculture and Agri-Food Canada, Ottawa, Ontario, Canada.
authors.forename: Z Q
authors.initials: ZQ
authors.lastname: Shao
authors.forename: R
authors.initials: R
authors.lastname: Behki
mesh_terms: D001280:Atrazine / Q000494:pharmacology; D001483:Base Sequence; D001673:Biodegradation, Environmental; D002235:Carbofuran / Q000494:pharmacology; D003001:Cloning, Molecular; D003470:Culture Media; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D015870:Gene Expression / Q000187:drug effects; D005798:Genes, Bacterial; D005947:Glucose / Q000494:pharmacology; D006540:Herbicides / Q000378:metabolism / Q000494:pharmacology; D007306:Insecticides / Q000494:pharmacology; D007763:Lac Operon; D008969:Molecular Sequence Data; D010575:Pesticides / Q000378:metabolism* / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012240:Rhodococcus / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D012839:Simazine / Q000494:pharmacology; D013859:Thiocarbamates / Q000378:metabolism / Q000494:pharmacology
chemical_list: D003470:Culture Media; D004269:DNA, Bacterial; D006540:Herbicides; D007306:Insecticides; D010575:Pesticides; D011993:Recombinant Fusion Proteins; D013859:Thiocarbamates; D003577:Cytochrome P-450 Enzyme System; D005947:Glucose; D001280:Atrazine; C036251:EPTC; D012839:Simazine; D002235:Carbofuran