Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA.
J Mol Biol. 2011 Oct 7;412(5):754-71. doi: 10.1016/j.jmb.2011.01.018. Epub 2011 Mar 1.
Initiation of RNA synthesis from DNA templates by RNA polymerase (RNAP) is a multi-step process, in which initial recognition of promoter DNA by RNAP triggers a series of conformational changes in both RNAP and promoter DNA. The bacterial RNAP functions as a molecular isomerization machine, using binding free energy to remodel the initial recognition complex, placing downstream duplex DNA in the active site cleft and then separating the nontemplate and template strands in the region surrounding the start site of RNA synthesis. In this initial unstable "open" complex the template strand appears correctly positioned in the active site. Subsequently, the nontemplate strand is repositioned and a clamp is assembled on duplex DNA downstream of the open region to form the highly stable open complex, RP(o). The transcription initiation factor, σ(70), plays critical roles in promoter recognition and RP(o) formation as well as in early steps of RNA synthesis.
DNA 模板上的 RNA 聚合酶 (RNAP) 启动 RNA 合成是一个多步骤的过程，其中 RNAP 对启动子 DNA 的初步识别触发了 RNAP 和启动子 DNA 的一系列构象变化。细菌 RNAP 作为一种分子异构化机器，利用结合自由能重塑初始识别复合物，将下游双链 DNA 置于活性位点裂缝中，然后在 RNA 合成起始位点周围的区域中分离非模板和模板链。在这个最初不稳定的“开放”复合物中，模板链在活性位点中正确定位。随后，非模板链重新定位，并在开放区域下游的双链 DNA 上组装一个夹子以形成高度稳定的开放复合物，RP(o)。转录起始因子 σ(70) 在启动子识别、RP(o) 形成以及 RNA 合成的早期步骤中发挥关键作用。
