Lehrstuhl Biopolymere und Forschungszentrum für Bio-Makromoleküle, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.
Structure. 2011 Jul 13;19(7):945-54. doi: 10.1016/j.str.2011.03.024.
Elongating Escherichia coli RNAP is modulated by NusA protein. The C-terminal domain (CTD) of the RNAP α subunit (αCTD) interacts with the acidic CTD 2 (AR2) of NusA, releasing the autoinhibitory blockade of the NusA S1-KH1-KH2 motif and allowing NusA to bind nascent nut spacer RNA. We determined the solution conformation of the AR2:αCTD complex. The αCTD residues that interface with AR2 are identical to those that recognize UP promoter elements A nusA-ΔAR2 mutation does not affect UP-dependent rrnH transcription initiation in vivo. Instead, the mutation inhibits Rho-dependent transcription termination at phage λtR1, which lies adjacent to the λnutR sequence. The Rho-dependent λtimm terminator, which is not preceded by a λnut sequence, is fully functional. We propose that constitutive binding of NusA-ΔAR2 to λnutR occludes Rho. In addition, the mutation confers a dominant defect in exiting stationary phase.
NusA 蛋白调节大肠杆菌 RNA 聚合酶的延伸。RNA 聚合酶 α 亚基（αCTD）的 C 端结构域（CTD）与 NusA 的酸性 CTD2（AR2）相互作用，释放 NusA S1-KH1-KH2 基序的自动抑制阻断，从而允许 NusA 结合新生的间隔 RNA。我们确定了 AR2:αCTD 复合物的溶液构象。与 AR2 相互作用的 αCTD 残基与识别 UP 启动子元件的残基相同，A nusA-ΔAR2 突变不会影响体内依赖 UP 的 rrnH 转录起始。相反，该突变抑制了紧邻 λnutR 序列的噬菌体 λtR1 处的 Rho 依赖性转录终止。不被 λnut 序列先导的 Rho 依赖性 λtimm 终止子完全有功能。我们提出，NusA-ΔAR2 与 λnutR 的组成性结合会阻碍 Rho。此外，该突变赋予了在静止期退出的显性缺陷。
