Ding Zhanyu, Xu Cong, Sahu Indrajit, Wang Yifan, Fu Zhenglin, Huang Min, Wong Catherine C L, Glickman Michael H, Cong Yao
National Center for Protein Science Shanghai, State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 201210, China; Shanghai Science Research Center, Chinese Academy of Sciences, Shanghai 201210, China.
National Center for Protein Science Shanghai, State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 201210, China.
Mol Cell. 2019 Mar 21;73(6):1150-1161.e6. doi: 10.1016/j.molcel.2019.01.018. Epub 2019 Feb 18.
The 26S proteasome is the ATP-dependent protease responsible for regulating the proteome of eukaryotic cells through degradation of mainly ubiquitin-tagged substrates. In order to understand how proteasome responds to ubiquitin signal, we resolved an ensemble of cryo-EM structures of proteasome in the presence of K48-Ub, with three of them resolved at near-atomic resolution. We identified a conformation with stabilized ubiquitin receptors and a previously unreported orientation of the lid, assigned as a Ub-accepted state C1-b. We determined another structure C3-b with localized K48-Ub to the toroid region of Rpn1, assigned as a substrate-processing state. Our structures indicate that tetraUb induced conformational changes in proteasome could initiate substrate degradation. We also propose a CP gate-opening mechanism involving the propagation of the motion of the lid to the gate through the Rpn6-α2 interaction. Our results enabled us to put forward a model of a functional cycle for proteasomes induced by tetraUb and nucleotide.
26S蛋白酶体是一种依赖ATP的蛋白酶，主要通过降解泛素标记的底物来调节真核细胞的蛋白质组。为了了解蛋白酶体如何响应泛素信号，我们解析了在K48-Ub存在下蛋白酶体的一系列冷冻电镜结构，其中三个结构的分辨率接近原子分辨率。我们鉴定出一种泛素受体稳定且盖子呈先前未报道取向的构象，命名为Ub接受态C1-b。我们还确定了另一种结构C3-b，其中K48-Ub定位于Rpn1的环形区域，命名为底物加工态。我们的结构表明，四聚泛素诱导的蛋白酶体构象变化可启动底物降解。我们还提出了一种CP门开放机制，该机制涉及盖子的运动通过Rpn6-α2相互作用传递到门。我们的结果使我们能够提出一个由四聚泛素和核苷酸诱导的蛋白酶体功能循环模型。
