The 13Å structure of a chaperonin GroEL-protein substrate complex by cryo-electron microscopy
The 13Å structure of a chaperonin GroEL-protein substrate complex by cryo-electron microscopy
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DOI：
10.1016/j.jmb.2005.02.027
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发表时间：
2005-04-22
影响因子：
5.6
通讯作者：
Fisher, MT
中科院分区：
文献类型：
--
作者：
Falke, S;Tama, F;Fisher, MT
GroEL结合到蛋白质底物谷氨酰胺合成酶（GS（m））的单个单体的13埃分辨率结构，以及未配体化的GroEL的13埃分辨率结构已经使用低温电子显微镜（cryo-EM）结合单粒子图像分类和重建技术从异质图像群体中确定。我们结合了来自cryo-EM图和动态建模的结构数据，利用已知的X射线晶体学结构和正常模式灵活拟合（NMFF）分析，来描述GS（m）结合引起的GroEL结构中发生的变化。NMFF分析揭示了由GS（m）结合诱导的分子运动在整个GroEL结构中传播。模拟的分子运动表明，一些领域进行整体运动，而其他人则表现出更复杂的独立的内部运动。有趣的是，顺式（GS（m）结合环）和反式（相反的无底物环）的底物结合顶端结构域均显示逆时针旋转，方向与ATP-GroEL诱导的结构变化相同（尽管不那么显著）。GroEL环之间的变构底物蛋白诱导的负协同性的结构变化涉及顺式和反式赤道结构域向GS（m）结合环的向上协同运动，同时保持七聚体接触残基之间的环间距离。此外，NMFF分析鉴定了在未结合的反式环中观察到的空腔开口直径减小约5埃中涉及的二级结构元件。了解这些底物蛋白诱导的七聚体环结构变化的分子基础，可以深入了解长距离（类似于140埃）传输的变构负协同效应的起源。(c)2005爱思唯尔有限公司保留所有权利。
The 13 angstrom resolution structures of GroEL bound to a single monomer of the protein substrate glutamine synthetase (GS(m)), as well as that of unliganded GroEL have been determined from a heterogeneous image population using cryo-electron microscopy (cryo-EM) coupled with single-particle image classification and reconstruction techniques. We combined structural data from cryo-EM maps and dynamic modeling, taking advantage of the known X-ray crystallographic structure and normal mode flexible fitting (NMFF) analysis, to describe the changes that occur in GroEL structure induced by GS(m) binding. The NMFF analysis reveals that the molecular movements induced by GS(m) binding propagate throughout the GroEL structure. The modeled molecular motions show that some domains undergo en bloc movements, while others show more complex independent internal movements. Interestingly, the substrate-bound apical domains of both the cis (GS(m)-bound ring) and trans (the opposite substrate-free ring) show counterclockwise rotations, in the same direction (though not as dramatic) as those documented for the ATP-GroEL-induced structure changes. The structural changes from the allosteric substrate protein-induced negative cooperativity between the GroEL rings involves upward concerted movements of both cis and trans equatorial domains toward the GS(m)-bound ring, while the inter-ring distances between the heptamer contact residues are maintained. Furthermore, the NMFF analysis identifies the secondary structural elements that are involved in the observed similar to 5 angstrom reduction in the diameter of the cavity opening in the unbound trans ring. Understanding the molecular basis of these substrate protein-induced structural changes across the heptamer rings provides insight into the origins of the allosteric negative cooperative effects that are transmitted over long distances (similar to 140 angstrom). (c) 2005 Elsevier Ltd. All rights reserved.