Structural basis for dynamic regulation of the human 26S proteasome
Structural basis for dynamic regulation of the human 26S proteasome
复制标题
人类26S蛋白酶体动态调控的结构基础
DOI：
10.1073/pnas.1614614113
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发表时间：
2016-11-15
影响因子：
11.1
通讯作者：
Mao, Youdong
中科院分区：
文献类型：
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作者：
Chen, Shuobing;Wu, Jiayi;Mao, Youdong
蛋白酶体全酶是真核生物中的一种ATP依赖性蛋白酶，降解泛素化底物。它参与许多重要的生物学过程，如细胞分裂、分化、先天免疫、获得性免疫、基因表达调节和对蛋白毒性应激的应答。使用冷冻电子显微镜，我们已经研究了多种构象状态的人类蛋白酶体在中到高分辨率。我们的研究结果表明，在核心颗粒的衬底导电通道是瞬时打开，并伴随着动态变化的颗粒结构。这些观察结果为蛋白酶体如何识别遍在化底物并将其通过通道和门转移到核心颗粒中的降解位点提供了新的见解。蛋白酶体是所有真核细胞中蛋白质降解的主要引擎。该机器的核心是AAA（与多种细胞活性相关的ATP酶）蛋白的异六聚体环，其展开泛素化的靶蛋白，所述靶蛋白同时易位到蛋白水解室中并降解成肽。使用冷冻电子显微镜，我们确定了近原子分辨率的2.5-MDa的人类蛋白酶体在其基态的结构，以及亚纳米分辨率的结构的全酶在三个可选的构象状态。底物展开的AAA-ATP酶通道由10个向内的孔环变窄，孔环排列成两个平行的螺旋，一个具有疏水性，另一个具有高电荷。人们意外地发现，核心粒子的门在基态是关闭的，而在另一种状态中只有一种是打开的。协调的，逐步的构象变化的调节颗粒耦合ATP水解底物易位和调节门控的核心颗粒，导致进行性降解。
Significance The proteasome holoenzyme is an ATP-dependent protease in eukaryotes that degrades ubiquitylated substrates. It is involved in numerous important biological processes, such as cell division, differentiation, innate immunity, adaptive immunity, regulation of gene expression, and response to proteotoxic stress. Using cryoelectron microscopy, we have examined multiple conformational states of the human proteasome at medium to high resolution. Our results reveal that the substrate-conducting channel in the core particle is transiently opened and accompanied by dynamic changes in structure of the particle. These observations provide new insights into how the proteasome recognizes ubiquitylated substrates and translocates them through a channel and gate to degradation sites in the core particle. The proteasome is the major engine of protein degradation in all eukaryotic cells. At the heart of this machine is a heterohexameric ring of AAA (ATPases associated with diverse cellular activities) proteins that unfolds ubiquitylated target proteins that are concurrently translocated into a proteolytic chamber and degraded into peptides. Using cryoelectron microscopy, we determined a near–atomic-resolution structure of the 2.5-MDa human proteasome in its ground state, as well as subnanometer-resolution structures of the holoenzyme in three alternative conformational states. The substrate-unfolding AAA-ATPase channel is narrowed by 10 inward-facing pore loops arranged into two helices that run in parallel with each other, one hydrophobic in character and the other highly charged. The gate of the core particle was unexpectedly found closed in the ground state and open in only one of the alternative states. Coordinated, stepwise conformational changes of the regulatory particle couple ATP hydrolysis to substrate translocation and regulate gating of the core particle, leading to processive degradation.