Structural basis of ClpXP recognition and unfolding of ssrA-tagged substrates.
Structural basis of ClpXP recognition and unfolding of ssrA-tagged substrates.
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DOI：
10.7554/elife.61496
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发表时间：
2020-10-22
期刊：
影响因子：
7.7
通讯作者：
Sauer RT
中科院分区：
文献类型：
--
作者：
Fei X;Bell TA;Barkow SR;Baker TA;Sauer RT
当核糖体无法完成正常翻译时，所有细胞都有机制确保所得部分蛋白质降解，以保护蛋白质组的完整性。在大肠杆菌和其他真细菌中，tmRNA 系统可挽救停滞的核糖体，并在不完整蛋白质的 C 末端添加 ssrA 标签或降解决定子，从而指导 AAA+ ClpXP 蛋白酶进行降解。在这里，我们展示了与 ssrA 降解子结合的 ClpXP 的冷冻电镜结构。 ssrA 降解决定子的 C 端残基最初结合在封闭的 ClpX 轴向通道的顶部，随后更深入地进入开放通道。对于短降解决定子蛋白质底物，我们表明解折叠可以直接从最初的封闭通道复合物发生。对于较长的降解决定子底物，我们的研究阐明了 ClpXP 如何从特异性识别转变为非特异性解折叠和易位机器。许多 AAA+ 蛋白酶和蛋白质重塑马达可能采用类似的多步骤识别和参与策略。
When ribosomes fail to complete normal translation, all cells have mechanisms to ensure degradation of the resulting partial proteins to safeguard proteome integrity. In Escherichia coli and other eubacteria, the tmRNA system rescues stalled ribosomes and adds an ssrA tag or degron to the C-terminus of the incomplete protein, which directs degradation by the AAA+ ClpXP protease. Here, we present cryo-EM structures of ClpXP bound to the ssrA degron. C-terminal residues of the ssrA degron initially bind in the top of an otherwise closed ClpX axial channel and subsequently move deeper into an open channel. For short-degron protein substrates, we show that unfolding can occur directly from the initial closed-channel complex. For longer degron substrates, our studies illuminate how ClpXP transitions from specific recognition into a nonspecific unfolding and translocation machine. Many AAA+ proteases and protein-remodeling motors are likely to employ similar multistep recognition and engagement strategies.