A 2.1-angstrom-resolution crystal structure of unliganded CRM1 reveals the mechanism of autoinhibition
A 2.1-angstrom-resolution crystal structure of unliganded CRM1 reveals the mechanism of autoinhibition
复制标题
未配体 CRM1 的 2.1 埃分辨率晶体结构揭示了自抑制机制
DOI：
10.1016/j.jmb.2012.11.014
复制
发表时间：
2013
期刊：
影响因子：
--
通讯作者：
N.
中科院分区：
文献类型：
--
作者：
Saito;N.
CRM1介导大量含有富含亮氨酸的核输出信号(NES)的蛋白质和核糖核蛋白的核输出。RanGTP与细胞核中CRM1的结合稳定了与CRM1的货物结合，反之亦然，但RanGTP和NES与CRM1结合的正协同作用机制尚不完全清楚。在这里，我们报道了未连接的酿酒酵母CRM1(Xpo1p)的2.1？分辨率晶体结构，该结构表明CRM1的一个内环(称为HEAT9环)主要负责将NES结合裂隙维持在封闭的构象中，使CRM1在没有RanGTP的情况下不能与NES结合。该结构还表明，CRM1的C-末端尾部稳定了HEAT9环的自抑制构象，从而加强了自抑制。与CRM1-NES-RanGTP络合物的结构比较揭示了RanGTP的结合是如何与CRM1的一系列变构构象变化相关联的，这些变化导致NES结合裂缝的打开，从而使NES货物能够稳定地结合。
CRM1 mediates nuclear export of numerous proteins and ribonucleoproteins containing a leucine-rich nuclear export signal (NES). Binding of RanGTP to CRM1 in the nucleus stabilizes cargo association with CRM1, and vice versa, but the mechanism underlying the positive cooperativity in RanGTP and NES binding to CRM1 remains incompletely understood. Herein we report a 2.1-Å-resolution crystal structure of unliganded Saccharomyces cerevisiae CRM1 (Xpo1p) that demonstrates that an internal loop of CRM1 (referred to as HEAT9 loop) is primarily responsible for maintaining the NES-binding cleft in a closed conformation, rendering CRM1 incapable of NES binding in the absence of RanGTP. The structure also shows that the C-terminal tail of CRM1 stabilizes the autoinhibitory conformation of the HEAT9 loop and thereby reinforces autoinhibition. Comparison with the structures of CRM1–NES–RanGTP complexes reveals how binding of RanGTP is associated with a series of allosteric conformational changes in CRM1 that lead to opening of the NES-binding cleft, allowing for stable binding of NES cargoes.