Abstract：
Activated FXII (FXIIa) is the principal initiator of the plasma contact system and can activate both procoagulant and proinflammatory pathways. Its activity is important in the pathophysiology of hereditary angioedema (HAE). Here, we describe a high-resolution cryoelectron microscopy (cryo-EM) structure of the beta-chain from FXIIa (βFXIIa) complexed with the Fab fragment of garadacimab. Garadacimab binds to βFXIIa through an unusually long CDR-H3 that inserts into the S1 pocket in a non-canonical way. This structural mechanism is likely the primary contributor to the inhibition of activated FXIIa proteolytic activity in HAE. Garadacimab Fab-βFXIIa structure also reveals critical determinants of high-affinity binding of garadacimab to activated FXIIa. Structural analysis with other bona fide FXIIa inhibitors, such as benzamidine and C1-INH, reveals a surprisingly similar mechanism of βFXIIa inhibition by garadacimab. In summary, the garadacimab Fab-βFXIIa structure provides crucial insights into its mechanism of action and delineates primary and auxiliary paratopes/epitopes.
摘要：
激活的FXII(FXIIa)是血浆接触系统的主要引发剂,并且可以激活促凝血和促炎途径。其活性在遗传性血管性水肿（HAE）的病理生理学中很重要。这里,我们描述了与garadacimab的Fab片段复合的FXIIa（βFXIIa）的β链的高分辨率低温电子显微镜（cryo-EM）结构。Garadacimab通过异常长的CDR-H3与βFXIIa结合，该CDR-H3以非规范方式插入S1口袋。这种结构机制可能是抑制HAE中活化的FXIIa蛋白水解活性的主要贡献者。GaradacimabFab-βFXIIa结构还揭示了garadacimab与活化的FXIIa的高亲和力结合的关键决定因素。用其他真正的FXIIa抑制剂进行结构分析，如苄脒和C1-INH，揭示了garadacimab抑制βFXIIa的惊人相似机制。总之,garadacimabFab-βFXIIa结构提供了对其作用机制的重要见解，并描述了主要和辅助互补位/表位。
