Cloning and expression in Escherichia coli of a Klebsiella ozaenae plasmid-borne gene encoding a nitrilase specific for the herbicide bromoxynil.
An enzyme (nitrilase) that converts the herbicide bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) to its metabolite 3,5-dibromo-4-hydroxybenzoic acid was shown to be plasmid encoded in the natural soil isolate Klebsiella ozaenae. The bromoxynil-specific nitrilase was expressed in Escherichia coli by direct transfer and stable maintenance in E. coli of a naturally occurring 82-kilobase K. ozaenae plasmid. Irreversible loss of the ability to metabolize bromoxynil both in E. coli and K. ozaenae was associated with the conversion of the 82-kilobase plasmid to a 68-kilobase species. In E. coli this conversion was the result of a host recA+-dependent recombinational event. A gene, designated bxn, encoding the bromoxynil-specific nitrilase was constitutively expressed in K. ozaenae and E. coli and subcloned on a 2.6-kilobase PstI DNA segment. The polarity and the location of the gene were determined by assaying hybrid constructs of the bromoxynil-specific nitrilase gene fused with the heterologous lac promoter.
D000619:Aminohydrolases / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D004926:Escherichia coli / Q000235:genetics*; D005796:Genes; D005798:Genes, Bacterial; D007709:Klebsiella / Q000201:enzymology / Q000235:genetics*; D010957:Plasmids; D014158:Transcription, Genetic
D004262:DNA Restriction Enzymes; D000619:Aminohydrolases; C076915:bromoxynil nitrilase