Structural basis of transcription:: An RNA polymerase II elongation complex at 3.3 Ã… resolution
Structural basis of transcription:: An RNA polymerase II elongation complex at 3.3 Ã… resolution
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DOI：
10.1126/science.1059495
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发表时间：
2001-06-08
期刊：
影响因子：
56.9
通讯作者：
Kornberg, RD
中科院分区：
文献类型：
--
作者：
Gnatt, AL;Cramer, P;Kornberg, RD
在3.3埃分辨率下测定转录过程中RNA聚合酶II的晶体结构。双链体DNA进入酶的主要裂缝，并在活性位点之前解旋。DNA-RNA杂交体的9个碱基对从活性中心以近直角延伸到进入的DNA，RNA的3'端位于核苷酸添加位点。3'端位于孔上方，核苷酸可以通过该孔进入，并且RNA可以在回溯期间通过该孔挤出。RNA的最5 '端残基靠近出口沟的入口点。转录复合物和游离酶之间的蛋白质结构的变化包括DNA和RNA上的钳的闭合以及在钳的基部的一系列“开关”的排序，以产生与DNA-RNA杂合体互补的结合位点。蛋白质-核酸接触有助于解释DNA和RNA链分离、RNA合成的特异性、转录起始期间的“流产循环”以及转录延伸期间的RNA和DNA易位。
The crystal structure of RNA polymerase II in the act of transcription was determined at 3.3 Angstrom resolution. Duplex DNA is seen entering the main cleft of the enzyme and unwinding before the active site. Nine base pairs of DNA-RNA hybrid extend from the active center at nearly right angles to the entering DNA, with the 3' end of the RNA in the nucleotide addition site. The 3' end is positioned above a pore, through which nucleotides may enter and through which RNA may be extruded during back-tracking. The 5'-most residue of the RNA is close to the point of entry to an exit groove. Changes in protein structure between the transcribing complex and free enzyme include closure of a clamp over the DNA and RNA and ordering of a series of "switches" at the base of the clamp to create a binding site complementary to the DNA-RNA hybrid. Protein-nucleic acid contacts help explain DNA and RNA strand separation, the specificity of RNA synthesis, "abortive cycling" during transcription initiation, and RNA and DNA translocation during transcription elongation.