PDF(Pubmed)
Abstract：
The E3 ligase-degron interaction determines the specificity of the ubiquitin‒proteasome system. We recently discovered that FEM1B, a substrate receptor of Cullin 2-RING ligase (CRL2), recognizes C-degrons containing a C-terminal proline. By solving several cryo-EM structures of CRL2FEM1B bound to different C-degrons, we elucidate the dimeric assembly of the complex. Furthermore, we reveal distinct dimerization states of unmodified and neddylated CRL2FEM1B to uncover the NEDD8-mediated activation mechanism of CRL2FEM1B. Our research also indicates that, FEM1B utilizes a bipartite mechanism to recognize both the C-terminal proline and an upstream aromatic residue within the substrate. These structural findings, complemented by in vitro ubiquitination and in vivo cell-based assays, demonstrate that CRL2FEM1B-mediated polyubiquitination and subsequent protein turnover depend on both FEM1B-degron interactions and the dimerization state of the E3 ligase complex. Overall, this study deepens our molecular understanding of how Cullin-RING E3 ligase substrate selection mediates protein turnover.
摘要：
E3连接酶-degron相互作用决定了泛素-蛋白酶体系统的特异性。我们最近发现FEM1B,Cullin2-RING连接酶（CRL2）的底物受体，识别包含C末端脯氨酸的C-degrons。通过求解与不同C-degrons结合的CRL2FEM1B的几种低温-EM结构，我们阐明了复杂的二聚体组装。此外，我们揭示了未修饰和内化的CRL2FEM1B的不同二聚化状态，以揭示NEDD8介导的CRL2FEM1B激活机制。我们的研究还表明,FEM1B利用两部分机制来识别底物内的C末端脯氨酸和上游芳族残基。这些结构性发现，补充体外泛素化和体内基于细胞的测定，证明CRL2FEM1B介导的多泛素化和随后的蛋白质周转取决于FEM1B-degron相互作用和E3连接酶复合物的二聚化状态。总的来说,这项研究加深了我们对Cullin-RINGE3连接酶底物选择如何介导蛋白质周转的分子理解。
