Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried 82152, Germany.
Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, Martinsried 82152, Germany.
Mol Cell. 2021 Jun 3;81(11):2445-2459.e13. doi: 10.1016/j.molcel.2021.03.025. Epub 2021 Apr 26.
How are E3 ubiquitin ligases configured to match substrate quaternary structures? Here, by studying the yeast GID complex (mutation of which causes deficiency in glucose-induced degradation of gluconeogenic enzymes), we discover supramolecular chelate assembly as an E3 ligase strategy for targeting an oligomeric substrate. Cryoelectron microscopy (cryo-EM) structures show that, to bind the tetrameric substrate fructose-1,6-bisphosphatase (Fbp1), two minimally functional GID E3s assemble into the 20-protein Chelator-GID, which resembles an organometallic supramolecular chelate. The Chelator-GID assembly avidly binds multiple Fbp1 degrons so that multiple Fbp1 protomers are simultaneously ubiquitylated at lysines near the allosteric and substrate binding sites. Importantly, key structural and biochemical features, including capacity for supramolecular assembly, are preserved in the human ortholog, the CTLH E3. Based on our integrative structural, biochemical, and cell biological data, we propose that higher-order E3 ligase assembly generally enables multipronged targeting, capable of simultaneously incapacitating multiple protomers and functionalities of oligomeric substrates.
E3 泛素连接酶如何匹配底物的四级结构？在这里，通过研究酵母 GID 复合物（该复合物的突变会导致糖异生酶在葡萄糖诱导下的降解不足），我们发现超分子螯合组装是一种 E3 连接酶策略，可用于靶向寡聚底物。冷冻电子显微镜（cryo-EM）结构表明，为了结合四聚体底物果糖-1,6-二磷酸酶（Fbp1），两个功能最小的 GID E3 组装成 20 个蛋白的 Chelator-GID，类似于有机金属超分子螯合物。Chelator-GID 组装物能强烈结合多个 Fbp1 降解结构域，从而使多个 Fbp1 原聚体在别构和底物结合位点附近的赖氨酸上同时被泛素化。重要的是，包括超分子组装能力在内的关键结构和生化特征在人类同源物 CTLH E3 中得以保留。基于我们的综合结构、生化和细胞生物学数据，我们提出，更高阶的 E3 连接酶组装通常能够实现多方位靶向，能够同时使多个原聚体和寡聚底物的功能失效。
