Essential role of the chaperonin folding compartment in vivo
Essential role of the chaperonin folding compartment in vivo
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DOI：
10.1038/emboj.2008.77
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发表时间：
2008-05-21
期刊：
影响因子：
11.4
通讯作者：
Hayer-Hartl, Manajit
中科院分区：
文献类型：
--
作者：
Tang, Yun-Chi;Chang, Hung-Chun;Hayer-Hartl, Manajit
大肠杆菌的GroEL/Groes伴侣蛋白系统形成了一个纳米笼子，允许单个蛋白质分子在隔离的情况下折叠。然而，由于伴侣蛋白也可以独立于底物包裹而介导折叠，目前尚不清楚折叠笼是否在体内是必需的。为了解决这个问题，我们用GroEL的突变体取代了野生型GroEL，这些突变体要么减少了笼子的体积，要么改变了笼壁的电荷性质。尽管突变体有效地结合了非天然蛋白，但笼子大小的逐步减小会导致细胞活力的逐渐丧失。值得注意的是，笼子尺寸的温和减小增加了产量和绿色荧光蛋白折叠的表观速率，这与空间位阻效应可以加速折叠的观点一致。在体外，观察到的折叠加速依赖于GroES对蛋白质的包裹，但与GroEL ATPase调节的Groes循环无关。改变GroEL笼壁的净负电荷也强烈影响伴侣功能。基于这些发现，GroEL/GroES间隔是蛋白质在体内折叠所必需的。
The GroEL/GroES chaperonin system of Escherichia coli forms a nano-cage allowing single protein molecules to fold in isolation. However, as the chaperonin can also mediate folding independently of substrate encapsulation, it remained unclear whether the folding cage is essential in vivo. To address this question, we replaced wild-type GroEL with mutants of GroEL having either a reduced cage volume or altered charge properties of the cage wall. A stepwise reduction in cage size resulted in a gradual loss of cell viability, although the mutants bound non-native protein efficiently. Strikingly, a mild reduction in cage size increased the yield and the apparent rate of green fluorescent protein folding, consistent with the view that an effect of steric confinement can accelerate folding. As shown in vitro, the observed acceleration of folding was dependent on protein encapsulation by GroES but independent of GroES cycling regulated by the GroEL ATPase. Altering the net-negative charge of the GroEL cage wall also strongly affected chaperonin function. Based on these findings, the GroEL/GroES compartment is essential for protein folding in vivo.