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首页> 外文期刊>Journal of bacteriology >Mechanism of Repression of the aroP P2 Promoter by the TyrR Protein of Escherichia coli
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Mechanism of Repression of the aroP P2 Promoter by the TyrR Protein of Escherichia coli

机译：大肠杆菌的TyrR蛋白抑制aroP P2启动子的机制

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摘要

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.
机译：以前，我们已经证明，在协同效应酪氨酸或苯丙氨酸的存在下，大肠杆菌aroP P2启动子的表达仅被TyrR蛋白部分抑制，而被TyrR蛋白强烈抑制（P. Wang， J. Yang和AJ Pittard，J。Bacteriol。179：4206–4212，1997）。在这里，我们目前的体外结果表明，TyrR蛋白和RNA聚合酶可以同时与 aroP P2启动子结合。在酪氨酸存在下，TyrR蛋白抑制P2启动子上开放复合物的形成，而在没有任何协同效应子或苯丙氨酸存在下，TyrR蛋白抑制开放复合物形成后的步骤。我们还提出了突变的证据，其牵涉到TyrR蛋白的N末端域抑制P2表达。 aroP 的TyrR结合位点位于P2转录起始位点下游5 bp，其中包括一个弱TyrR框和一个强TyrR框。突变分析的结果表明，强框（更靠近P2启动子），而不是弱框，在P2抑制中起关键作用。

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