title: Mechanism of repression of the aroP P2 promoter by the TyrR protein of Escherichia coli.
abstract: Previously, we have shown that expression of the Escherichia coli aroP P2 promoter is partially repressed by the TyrR protein alone and strongly repressed by the TyrR protein in the presence of the coeffector tyrosine or phenylalanine (P. Wang, J. Yang, and A. J. Pittard, J. Bacteriol. 179:4206-4212, 1997). Here we present in vitro results showing that the TyrR protein and RNA polymerase can bind simultaneously to the aroP P2 promoter. In the presence of tyrosine, the TyrR protein inhibits open complex formation at the P2 promoter, whereas in the absence of any coeffector or in the presence of phenylalanine, the TyrR protein inhibits a step(s) following the formation of open complexes. We also present mutational evidence which implicates the N-terminal domain of the TyrR protein in the repression of P2 expression. The TyrR binding site of aroP, which includes one weak and one strong TyrR box, is located 5 bp downstream of the transcription start site of P2. Results from a mutational analysis show that the strong box (which is located more closely to the P2 promoter), but not the weak box, plays a critical role in P2 repression.
authors.affiliation: Department of Microbiology, The University of Melbourne, Parkville, Victoria 3052, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Yang
authors.forename: P
authors.initials: P
authors.lastname: Wang
authors.forename: A J
authors.initials: AJ
authors.lastname: Pittard
mesh_terms: D026905:Amino Acid Transport Systems; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics*; D018983:DNA Footprinting; D003850:Deoxyribonuclease I / Q000378:metabolism; D004794:Enzyme Repression; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D026901:Membrane Transport Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D010649:Phenylalanine / Q000378:metabolism; D011196:Potassium Permanganate; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000378:metabolism*; D014158:Transcription, Genetic; D014443:Tyrosine / Q000378:metabolism
chemical_list: D026905:Amino Acid Transport Systems; C063201:AroP protein, E coli; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D012097:Repressor Proteins; C069256:TyrR protein, E coli; D011196:Potassium Permanganate; D014443:Tyrosine; D010649:Phenylalanine; D003850:Deoxyribonuclease I