Howard Hughes Medical Institute, Waksman Institute, and Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA.
Science. 2012 Aug 3;337(6094):591-5. doi: 10.1126/science.1218716.
Using single-molecule fluorescence resonance energy transfer, we have defined bacterial RNA polymerase (RNAP) clamp conformation at each step in transcription initiation and elongation. We find that the clamp predominantly is open in free RNAP and early intermediates in transcription initiation but closes upon formation of a catalytically competent transcription initiation complex and remains closed during initial transcription and transcription elongation. We show that four RNAP inhibitors interfere with clamp opening. We propose that clamp opening allows DNA to be loaded into and unwound in the RNAP active-center cleft, that DNA loading and unwinding trigger clamp closure, and that clamp closure accounts for the high stability of initiation complexes and the high stability and processivity of elongation complexes.
利用单分子荧光共振能量转移技术，我们在转录起始和延伸的每个步骤中定义了细菌 RNA 聚合酶 (RNAP) 夹的构象。我们发现，在游离 RNAP 和转录起始的早期中间物中，夹主要是开放的，但在形成催化有效的转录起始复合物时会关闭，并在初始转录和转录延伸过程中保持关闭。我们表明，有四种 RNAP 抑制剂会干扰夹的打开。我们提出，夹的打开允许 DNA 加载到 RNAP 活性中心裂隙中并解旋，DNA 加载和解旋触发夹的关闭，夹的关闭解释了起始复合物的高稳定性以及延伸复合物的高稳定性和持续性。
