Structure of the Cmr2-Cmr3 Subcomplex of the Cmr RNA Silencing Complex
Structure of the Cmr2-Cmr3 Subcomplex of the Cmr RNA Silencing Complex
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DOI：
10.1016/j.str.2013.01.002
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发表时间：
2013-03-05
期刊：
影响因子：
5.7
通讯作者：
Li, Hong
中科院分区：
文献类型：
--
作者：
Shao, Yaming;Cocozaki, Alexis I.;Li, Hong
Cmr复合物是一种RNA引导的效应子复合物，其在由CRISPR（重复的规则间隔短回文重复序列）-Cas系统介导的原核免疫应答中切割入侵RNA。在这里，我们报告的晶体结构的CMR subcomplex含有CMR 2（Cas 1 0）和CMR 3亚基在2.8埃的分辨率。该结构揭示了一个双重的铁氧还蛋白折叠和富含甘氨酸的循环特征，以前已知的重复相关的神秘蛋白和两个独特的插入元件在Cmr 3介导其与Cmr 2的相互作用。令人惊讶的是，虽然这两个插入元件的突变显着削弱Cmr 3-Cmr 2相互作用，它们表现出不同的影响Cmr介导的RNA切割的Cmr复合物，表明稳定的Cmr 2-Cmr 3相互作用的其他亚基。对Cmr 3的两个保守的（但非Cmr 2结合的）富含甘氨酸的环的进一步突变分析鉴定了可能参与Cmr复合物的组装或RNA切割功能的区域。
The Cmr complex is an RNA-guided effector complex that cleaves invader RNA in the prokaryotic immune response mediated by the CRISPR (Clustered Regularly Interspaced Short Palindromic Repeat)-Cas system. Here, we report the crystal structure of a Cmr subcomplex containing Cmr2 (Cas1 0) and Cmr3 subunits at 2.8 angstrom resolution. The structure revealed a dual ferredoxin fold and glycine-rich loops characteristic of previously known repeat-associated mysterious proteins and two unique insertion elements in Cmr3 that mediate its interaction with Cmr2. Surprisingly, while mutation of both insertion elements significantly weakened Cmr3-Cmr2 interaction, they exhibit differential effects on Cmr-mediated RNA cleavage by the Cmr complex, suggesting stabilization of Cmr2-Cmr3 interactions by other subunits. Further mutational analysis of the two conserved (but non-Cmr2-binding) glycine-rich loops of Cmr3 identified a region that is likely involved in assembly or the RNA cleavage function of the Cmr complex.