The nucleotide sequence of the tyrP promoter region from Escherichia coli has been determined. Two TYR R boxes have been identified, and one of these was shown to overlap the -35 region of a major tyrP promoter (pl). Si nuclease mapping of in vivo transcripts revealed that transcription from Pi is stimulated by phenylalanine and to a lesser extent by leucine. The demonstration that mutants in which TyrR-tyrosinemediated repression of tyrP has been abolished have single base changes in the TYR R box which overlaps Pi suggests that TyrR-tyrosine-mediated repression of tyrP also involves pl. TyrR-independent stimulation of tyrP expression by Casamino Acids involves a second promoter 140 bases upstream ofp1. There are no TYR R boxes in this region. The sequences of 10 TYR R boxes preceding the genes tyrP, MrR, and aroG and the operons aroF tyrA and aroL aroM are compared and discussed.
The gene tyrP, which codes for a component of the tyrosine-specific transport system, has been localized on the Escherichia coli K-12 chromosome at min 42. A tyrP-lac operon fusion was constructed and used to isolate mutants that have altered expression from the tyrP promoter. All putative tyrP operator mutations were transferred onto a plasmid vector by recombination in vivo. Restriction enzyme analysis of the resultant plasmids suggests that some of these mutants arose from either an insertion or a deletion of DNA occurring within the region of DNA that contains the tyrP promoter.
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