HECT ubiquitin ligases play essential roles in metazoan development and physiology. The HECT ligase HUWE1 is central to the cellular stress response by mediating degradation of key death or survival factors, including Mcl1, p53, DDIT4, and Myc. Although mutations in HUWE1 and related HECT ligases are widely implicated in human disease, our molecular understanding remains limited. Here we present a comprehensive investigation of full-length HUWE1, deepening our understanding of this class of enzymes. The N-terminal ∼3,900 amino acids of HUWE1 are indispensable for proper ligase function, and our cryo-EM structures of HUWE1 offer a complete molecular picture of this large HECT ubiquitin ligase. HUWE1 forms an alpha solenoid-shaped assembly with a central pore decorated with protein interaction modules. Structures of HUWE1 variants linked to neurodevelopmental disorders as well as of HUWE1 bound to a model substrate link the functions of this essential enzyme to its three-dimensional organization.

HECT 泛素连接酶在后生动物发育和生理学中发挥重要作用。HECT 连接酶 HUWE1 通过介导关键死亡或存活因子（包括 Mcl1、p53、DDIT4 和 Myc）的降解而成为细胞应激反应的核心。尽管 HUWE1 和相关 HECT 连接酶的突变广泛涉及人类疾病，但我们的分子理解仍然有限。在这里，我们对全长 HUWE1 进行了全面调查，加深了我们对此类酶的理解。HUWE1 的 N 端~3,900 个氨基酸对于正确的连接酶功能是必不可少的，我们的 HUWE1 冷冻电镜结构提供了这种大型 HECT 泛素连接酶的完整分子图。HUWE1 形成一个 alpha 螺线管形状的组件，其中心孔装饰有蛋白质相互作用模块。