Promoters and transcripts associated with the aroP gene of Escherichia coli.
Analysis of in vitro transcriptional events initiating within the region immediately upstream of the aroP coding region has revealed the presence of three promoters, P1, P2, and P3. Both P1 and P2 give rise to mRNA encoding the AroP protein, whereas P3 initiates transcription in the opposite direction. Both P1 and P3 contain UP elements which contribute to promoter strength. Regulation of expression from these three promoters has been examined in vitro by using supercoiled DNA templates and in vivo by using lacZ transcriptional fusions and specific promoter mutants. Expression from P2 is partially repressed by TyrR alone both in vitro and in vivo. Addition of the aromatic amino acid tyrosine, phenylalanine, or tryptophan further increases this repression. P1 is not repressed by TyrR alone but is repressed in vivo in the presence of phenylalanine, tyrosine, or tryptophan. This also occurs in vitro but requires Ca2+ ions in the reaction mixture for its demonstration. Under these conditions, transcription from P3 is enhanced by TyrR protein with phenylalanine, tyrosine, or tryptophan. However, we were unable to demonstrate P3 expression in vivo. Under repressing conditions, there is no production of truncated RNA molecules (from P1), which would be expected if repression involved a roadblock mechanism.
Wang
P
P
Department of Microbiology, University of Melbourne, Parkville, Victoria, Australia.
Yang
J
J
Pittard
A J
AJ
D026905:Amino Acid Transport Systems; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics*; D017931:DNA Primers; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial; D011993:Recombinant Fusion Proteins / Q000235:genetics; D014158:Transcription, Genetic; D012407:rRNA Operon
D026905:Amino Acid Transport Systems; C063201:AroP protein, E coli; D001426:Bacterial Proteins; D002352:Carrier Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D011993:Recombinant Fusion Proteins