Zhang G, Campbell E A, Minakhin L, Richter C, Severinov K, Darst S A
The Rockefeller University, New York, New York 10021, USA.
Cell. 1999 Sep 17;98(6):811-24. doi: 10.1016/s0092-8674(00)81515-9.
The X-ray crystal structure of Thermus aquaticus core RNA polymerase reveals a "crab claw"-shaped molecule with a 27 A wide internal channel. Located on the back wall of the channel is a Mg2+ ion required for catalytic activity, which is chelated by an absolutely conserved motif from all bacterial and eukaryotic cellular RNA polymerases. The structure places key functional sites, defined by mutational and cross-linking analysis, on the inner walls of the channel in close proximity to the active center Mg2+. Further out from the catalytic center, structural features are found that may be involved in maintaining the melted transcription bubble, clamping onto the RNA product and/or DNA template to assure processivity, and delivering nucleotide substrates to the active center.
嗜热水生栖热菌核心RNA聚合酶的X射线晶体结构揭示了一种呈“蟹爪”状的分子，其内部通道宽27埃。位于通道后壁的是催化活性所需的Mg2+离子，它由所有细菌和真核细胞RNA聚合酶中一个绝对保守的基序螯合。该结构将通过突变和交联分析确定的关键功能位点置于通道内壁，紧邻活性中心Mg2+。在离催化中心更远的地方，发现了一些结构特征，它们可能参与维持解链的转录泡、夹住RNA产物和/或DNA模板以确保持续合成能力，以及将核苷酸底物递送至活性中心。
