The carboxy-terminal coiled-coil of the RNA polymerase β′-subunit is the main binding site for Gre factors
The carboxy-terminal coiled-coil of the RNA polymerase β′-subunit is the main binding site for Gre factors
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DOI：
10.1038/sj.embor.7401079
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发表时间：
2007-11-01
期刊：
影响因子：
7.7
通讯作者：
Vassylyev, Dmitry G.
中科院分区：
文献类型：
--
作者：
Vassylyeva, Marina N.;Svetlov, Vladimir;Vassylyev, Dmitry G.
细菌Gre转录物切割因子刺激RNA聚合酶（RNAP）的内在核酸内切活性以拯救停滞的转录复合物。它们与RNAP结合并通过次级通道将其卷曲螺旋（CC）结构域延伸到催化中心。现有的三个模型的Gre-RNAP复杂假设一致的机制，Gre辅助催化，而提供相互矛盾的观点的Gre-RNAP相互作用。在这里，我们报告大肠杆菌的GreB结构。GreB单体形成三角形，其中一个分子的氨基末端CC的尖端被捕获在第二分子的羧基末端结构域的疏水腔内。这一安排表明，国家行动方案的征聘模式与此类似。事实上，位于二级通道边缘的β '-亚基CC在其尖端具有保守的疏水残基。我们表明，这些残基和那些在GreB的C-末端结构域腔的取代赋予缺陷GreB的活性和结合RNAP，并提出了一个合理的模型RNAP-GreB复合物。
Bacterial Gre transcript cleavage factors stimulate the intrinsic endonucleolytic activity of RNA polymerase ( RNAP) to rescue stalled transcription complexes. They bind to RNAP and extend their coiled- coil ( CC) domains to the catalytic centre through the secondary channel. Three existing models for the Gre - RNAP complex postulate congruent mechanisms of Gre- assisted catalysis, while offering conflicting views of the Gre - RNAP interactions. Here, we report the GreB structure of Escherichia coli. The GreB monomers form a triangle with the tip of the amino-terminal CC of one molecule trapped within the hydrophobic cavity of the carboxy- terminal domain of a second molecule. This arrangement suggests an analogous model for recruitment to RNAP. Indeed, the beta'- subunit CC located at the rim of the secondary channel has conserved hydrophobic residues at its tip. We show that substitutions of these residues and those in the GreB C- terminal domain cavity confer defects in GreB activity and binding to RNAP, and present a plausible model for the RNAP - GreB complex.