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首页> 外文期刊>Journal of Molecular Biology >Evidence for a tyrosine-adenine stacking interaction and for a short-lived open intermediate subsequent to initial binding of Escherichia coli RNA polymerase to promoter DNA.
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Evidence for a tyrosine-adenine stacking interaction and for a short-lived open intermediate subsequent to initial binding of Escherichia coli RNA polymerase to promoter DNA.

机译：大肠杆菌RNA聚合酶与启动子DNA初始结合后酪氨酸-腺嘌呤堆积相互作用和短寿命开放中间体的证据。

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摘要

Bacterial RNA polymerase and a "sigma" transcription factor form an initiation-competent "open" complex at a promoter by disruption of about 14 base pairs. Strand separation is likely initiated at the highly conserved -11 A-T base pair. Amino acids in conserved region 2.3 of the main Escherichia coli sigma factor, sigma(70), are involved in this process, but their roles are unclear. To monitor the fates of particular bases upon addition of RNA polymerase, promoters bearing single substitutions of the fluorescent A-analog 2-aminopurine (2-AP) at -11 and two other positions in promoter DNA were examined. Evidence was obtained for an open intermediate on the pathway to open complex formation, in which these 2-APs are no longer stacked onto their neighboring bases. The tyrosine at residue 430 in region 2.3 of sigma(70) was shown to be involved in quenching the fluorescence of a 2-AP substituted at -11, presumably through a stacking interaction. These data refine the structural model for open complex formation and reveal a novel interaction involved in DNA melting by RNA polymerase.
机译：细菌RNA聚合酶和“ sigma”转录因子通过破坏约14个碱基对在启动子上形成具有启动能力的“开放”复合物。高度保守的-11 A-T碱基对可能开始链分离。主要大肠杆菌sigma因子sigma（70）保守区2.3中的氨基酸参与了此过程，但其作用尚不清楚。为了监测添加RNA聚合酶后特定碱基的命运，检查了在-11和启动子DNA中两个其他位置带有荧光A类似物2-氨基嘌呤（2-AP）的单取代的启动子。已经获得了在打开复合物形成途径上的开放中间体的证据，其中这些2-AP不再堆叠在其相邻碱基上。 σ（70）区域2.3中第430位残基处的酪氨酸被证明与猝灭在-11处被取代的2-AP的荧光有关，大概是通过堆积相互作用。这些数据完善了开放复合物形成的结构模型，并揭示了RNA聚合酶参与DNA熔解的新型相互作用。

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