Murakami Katsuhiko S, Masuda Shoko, Campbell Elizabeth A, Muzzin Oriana, Darst Seth A
The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
Science. 2002 May 17;296(5571):1285-90. doi: 10.1126/science.1069595.
The crystal structure of Thermus aquaticus RNA polymerase holoenzyme (alpha2betabeta'omegasigmaA) complexed with a fork-junction promoter DNA fragment has been determined by fitting high-resolution x-ray structures of individual components into a 6.5-angstrom resolution map. The DNA lies across one face of the holoenzyme, completely outside the RNA polymerase active site channel. All sequence-specific contacts with core promoter elements are mediated by the sigma subunit. A universally conserved tryptophan is ideally positioned to stack on the exposed face of the base pair at the upstream edge of the transcription bubble. Universally conserved basic residues of the sigma subunit provide critical contacts with the DNA phosphate backbone and play a role in directing the melted DNA template strand into the RNA polymerase active site. The structure explains how holoenzyme recognizes promoters containing variably spaced -10 and -35 elements and provides the basis for models of the closed and open promoter complexes.
嗜热水生菌RNA聚合酶全酶（α2ββ′ωσA）与叉状连接启动子DNA片段复合物的晶体结构，是通过将各个组分的高分辨率X射线结构拟合到6.5埃分辨率图谱中确定的。DNA横跨全酶的一个面，完全位于RNA聚合酶活性位点通道之外。与核心启动子元件的所有序列特异性接触均由σ亚基介导。一个普遍保守的色氨酸处于理想位置，可堆积在转录泡上游边缘碱基对的暴露面上。σ亚基普遍保守的碱性残基与DNA磷酸主链形成关键接触，并在将解链的DNA模板链导入RNA聚合酶活性位点中发挥作用。该结构解释了全酶如何识别含有可变间距-10和-35元件的启动子，并为封闭和开放启动子复合物模型提供了基础。
