Fondazione Istituto FIRC di Oncologia Molecolare, Milan, Italy.
Nat Struct Mol Biol. 2013 Jun;20(6):696-701. doi: 10.1038/nsmb.2566. Epub 2013 May 5.
Homologous to E6-AP C terminus (HECT) E3 ligases recognize and directly catalyze ligation of ubiquitin (Ub) to their substrates. Molecular details of this process remain unknown. We report the first structure, to our knowledge, of a Ub-loaded E3, the human neural precursor cell-expressed developmentally downregulated protein 4 (Nedd4). The HECT(Nedd4)~Ub transitory intermediate provides a structural basis for the proposed sequential addition mechanism. The donor Ub, transferred from the E2, is bound to the Nedd4 C lobe with its C-terminal tail locked in an extended conformation, primed for catalysis. We provide evidence that the Nedd4-family members are Lys63-specific enzymes whose catalysis is mediated by an essential C-terminal acidic residue.
同源于 E6-AP C 末端（HECT）的 E3 连接酶识别并直接催化泛素（Ub）与其底物的连接。该过程的分子细节仍不清楚。我们报告了第一个结构，据我们所知，一个 Ub 负载的 E3，人类神经前体细胞表达的发育下调蛋白 4（Nedd4）。HECT（Nedd4）~Ub 瞬态中间物为所提出的顺序添加机制提供了结构基础。供体 Ub 从 E2 转移，与 Nedd4 的 C 叶结合，其 C 末端尾巴锁定在延伸构象中，为催化做好准备。我们提供的证据表明，Nedd4 家族成员是 Lys63 特异性酶，其催化由一个必需的 C 末端酸性残基介导。
