Murakami Katsuhiko S, Masuda Shoko, Darst Seth A
The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
Science. 2002 May 17;296(5571):1280-4. doi: 10.1126/science.1069594.
The crystal structure of the initiating form of Thermus aquaticus RNA polymerase, containing core RNA polymerase (alpha2betabeta'omega) and the promoter specificity sigma subunit, has been determined at 4 angstrom resolution. Important structural features of the RNA polymerase and their roles in positioning sigma within the initiation complex are delineated, as well as the role played by sigma in modulating the opening of the RNA polymerase active-site channel. The two carboxyl-terminal domains of sigma are separated by 45 angstroms on the surface of the RNA polymerase, but are linked by an extended loop. The loop winds near the RNA polymerase active site, where it may play a role in initiating nucleotide substrate binding, and out through the RNA exit channel. The advancing RNA transcript must displace the loop, leading to abortive initiation and ultimately to sigma release.
嗜热水生菌RNA聚合酶起始形式的晶体结构已在4埃分辨率下确定，该起始形式包含核心RNA聚合酶（α2ββ′ω）和启动子特异性σ亚基。文中描述了RNA聚合酶的重要结构特征及其在起始复合物中定位σ的作用，以及σ在调节RNA聚合酶活性位点通道开放中所起的作用。σ的两个羧基末端结构域在RNA聚合酶表面相距45埃，但通过一个延伸的环相连。该环在RNA聚合酶活性位点附近蜿蜒，可能在启动核苷酸底物结合中发挥作用，并穿出RNA出口通道。正在延伸的RNA转录物必须取代该环，导致流产起始并最终导致σ释放。
