Characterization of the Bacillus subtilis tryptophan promoter region

The nucleotide sequence of the control region of the trp operon of Bacillus subtilis has been determined. The region was shown to contain the trp promoter by deletion analysis and by determination of the transcription start site. The trp promoter shows similarity to the consensus sequence for Escherichia coli and B. subtilis promoters. The presence of the trp control region on a high-copy-number plasmid confers resistance to the tryptophan analogue 5-methyltryptophan. It appears that an approximately 120-base-pair region comprising not only the trp promoter but also adjacent direct repeat sequences is necessary to confer 5-methyltryptophan resistance. We postulate that this region is involved in tryptophan regulation and confers 5-methyltryptophan resistance by titration of a trp regulatory protein. Removal of either the trp promoter or the adjacent direct repeat sequences abolished the 5-methyltryptophan-resistance phenotype. Placement of unrelated promoters adjacent to the direct repeat sequences restored 5-methyltryptophan resistance. This suggests that promoter activity is necessary for the regulatory function.