Chaperonin complex with a newly folded protein encapsulated in the folding chamber.
Chaperonin complex with a newly folded protein encapsulated in the folding chamber.
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DOI：
10.1038/nature07479
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发表时间：
2009-01-01
期刊：
影响因子：
64.8
通讯作者：
Saibil, H. R.
中科院分区：
文献类型：
--
作者：
Clare, D. K.;Bakkes, P. J.;van Heerikhuizen, H.;van der Vies, S. M.;Saibil, H. R.
一部分必需的细胞蛋白需要伴侣蛋白的帮助（在大肠杆菌、GroEL和GroES中），这是一种双环复合物，其中两个环交替作用于结合、包裹和折叠新生或应激变性的蛋白质。这个过程开始于在GroEL环中心腔的疏水表面捕获底物蛋白。然后，ATP和co-chaperonin GroES结合到该环上，通过强制展开或其他主要构象变化，将非天然蛋白质从其结合位点喷射出来，并将其封闭在亲水腔中进行折叠。ATP水解和随后ATP与相反环的结合触发腔体的解离和底物蛋白的释放。T4噬菌体需要自身版本的GroES gp31， gp31形成一个更高的折叠室，以折叠主要的病毒衣壳蛋白gp23。多肽在伴侣蛋白复合体内折叠是已知的，但是包裹蛋白的构象以前还没有被可视化。在这里，我们展示了gp23-伴侣蛋白复合物的结构，显示了gp23被封装在折叠腔中的初始捕获状态和最终接近天然状态。尽管腔室扩大了，但它仍然不足以容纳延长的gp23单体，这解释了为什么GroEL-GroES复合体不能折叠gp23，并展示了伴侣蛋白结构如何扭曲以包裹一个大的生理底物蛋白。
A subset of essential cellular proteins requires the assistance of chaperonins (in E. coli, GroEL and GroES), double-ring complexes in which the two rings act alternately to bind, encapsulate and fold nascent or stress-denatured proteins. This process starts by the trapping of a substrate protein on hydrophobic surfaces in the central cavity of a GroEL ring. Then, binding of ATP and co-chaperonin GroES to that ring ejects the non-native protein from its binding sites, through forced unfolding or other major conformational changes, and encloses it in a hydrophilic chamber for folding. ATP hydrolysis and subsequent ATP binding to the opposite ring trigger dissociation of the chamber and release of the substrate protein. The bacteriophage T4 requires its own version of GroES, gp31, that forms a taller folding chamber, to fold the major viral capsid protein gp23. Polypeptides are known to fold inside the chaperonin complex, but the conformation of an encapsulated protein has not previously been visualized. Here we present structures of gp23-chaperonin complexes, showing both the initial captured state and the final, close-to-native state with gp23 encapsulated in the folding chamber. Although the chamber is expanded, it is still barely large enough to contain the elongated gp23 monomer, explaining why the GroEL-GroES complex is not able to fold gp23 and showing how the chaperonin structure distorts to enclose a large, physiological substrate protein.
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