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pubmed:abstractText |
The positively regulated nah and sal operons of the NAH7 plasmid from Pseudomonas putida encode the enzymes for metabolism of naphthalene via salicylate. To study their coordinate regulation, a 6-kb DNA fragment containing the entire nahA gene (encoding naphthalene dioxygenase), the gene of the nah operon, was cloned into a RSF1010 plasmid derivative. Analysis of expression of nahA from the nah promoter in either Escherichia coli or Pseudomonas putida showed that a 1.6-kb DNA fragment from the nahR (nah operon regulatory locus) region was required in trans for (i) induction by salicylate; (ii) high-level expression of nahA, and (iii) complementation of nahR- mutants. Measurement of transcription in induced and uninduced P. putida showed that induction of the nah and sal operons occurred at the transcriptional level. The trans-acting positive regulatory gene, nahR, however, was constitutively transcribed.
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