Scott Daniel C, Sviderskiy Vladislav O, Monda Julie K, Lydeard John R, Cho Shein Ei, Harper J Wade, Schulman Brenda A
Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Howard Hughes Medical Institute, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
Cell. 2014 Jun 19;157(7):1671-84. doi: 10.1016/j.cell.2014.04.037.
Most E3 ligases use a RING domain to activate a thioester-linked E2∼ubiquitin-like protein (UBL) intermediate and promote UBL transfer to a remotely bound target protein. Nonetheless, RING E3 mechanisms matching a specific UBL and acceptor lysine remain elusive, including for RBX1, which mediates NEDD8 ligation to cullins and >10% of all ubiquitination. We report the structure of a trapped RING E3-E2∼UBL-target intermediate representing RBX1-UBC12∼NEDD8-CUL1-DCN1, which reveals the mechanism of NEDD8 ligation and how a particular UBL and acceptor lysine are matched by a multifunctional RING E3. Numerous mechanisms specify cullin neddylation while preventing noncognate ubiquitin ligation. Notably, E2-E3-target and RING-E2∼UBL modules are not optimized to function independently, but instead require integration by the UBL and target for maximal reactivity. The UBL and target regulate the catalytic machinery by positioning the RING-E2∼UBL catalytic center, licensing the acceptor lysine, and influencing E2 reactivity, thereby driving their specific coupling by a multifunctional RING E3.
大多数E3连接酶利用一个RING结构域来激活硫酯连接的E2泛素样蛋白（UBL）中间体，并促进UBL转移到远距离结合的靶蛋白上。尽管如此，与特定UBL和受体赖氨酸相匹配的RING E3机制仍然难以捉摸，包括介导NEDD8与cullin连接以及所有泛素化反应中超过10%反应的RBX1。我们报道了一种捕获的RING E3-E2UBL-靶标中间体的结构，该中间体代表RBX1-UBC12NEDD8-CUL1-DCN1，它揭示了NEDD8连接的机制以及多功能RING E3如何匹配特定的UBL和受体赖氨酸。众多机制决定了cullin的NEDD化，同时防止非同源泛素连接。值得注意的是，E2-E3-靶标和RING-E2UBL模块并非为独立发挥功能而优化，而是需要通过UBL和靶标进行整合以实现最大反应活性。UBL和靶标通过定位RING-E2~UBL催化中心、使受体赖氨酸具备活性以及影响E2反应活性来调节催化机制，从而通过多功能RING E3驱动它们的特异性偶联。
