The dedicator of cytokinesis (DOCK)/engulfment and cell motility (ELMO) complex serves as a guanine nucleotide exchange factor (GEF) for the GTPase Rac. RhoG, another GTPase, activates the ELMO-DOCK-Rac pathway during engulfment and migration. Recent cryo-EM structures of the DOCK2/ELMO1 and DOCK2/ELMO1/Rac1 complexes have identified closed and open conformations that are key to understanding the autoinhibition mechanism. Nevertheless, the structural details of RhoG-mediated activation of the DOCK/ELMO complex remain elusive. Herein, we present cryo-EM structures of DOCK5/ELMO1 alone and in complex with RhoG and Rac1. The DOCK5/ELMO1 structure exhibits a closed conformation similar to that of DOCK2/ELMO1, suggesting a shared regulatory mechanism of the autoinhibitory state across DOCK-A/B subfamilies (DOCK1−5). Conversely, the RhoG/DOCK5/ELMO1/Rac1 complex adopts an open conformation that differs from that of the DOCK2/ELMO1/Rac1 complex, with RhoG binding to both ELMO1 and DOCK5. The alignment of the DOCK5 phosphatidylinositol (3,4,5)-trisphosphate binding site with the RhoG C-terminal lipidation site suggests simultaneous binding of RhoG and DOCK5/ELMO1 to the plasma membrane. Structural comparison of the apo and RhoG-bound states revealed that RhoG facilitates a closed-to-open state conformational change of DOCK5/ELMO1. Biochemical and surface plasmon resonance (SPR) assays confirm that RhoG enhances the Rac GEF activity of DOCK5/ELMO1 and increases its binding affinity for Rac1. Further analysis of structural variability underscored the conformational flexibility of the DOCK5/ELMO1/Rac1 complex core, potentially facilitating the proximity of the DOCK5 GEF domain to the plasma membrane. These findings elucidate the structural mechanism underlying the RhoG-induced allosteric activation and membrane binding of the DOCK/ELMO complex.

中文翻译：

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RhoG 促进鸟嘌呤核苷酸交换因子复合物 DOCK5/ELMO1 构象转变为开放状态


胞质分裂 (DOCK)/吞噬和细胞运动 (ELMO) 复合物的奉献者充当 GTPase Rac 的鸟嘌呤核苷酸交换因子 (GEF)。 RhoG 是另一种 GTP 酶，在吞噬和迁移过程中激活 ELMO-DOCK-Rac 通路。最近 DOCK2/ELMO1 和 DOCK2/ELMO1/Rac1 复合物的冷冻电镜结构已经确定了闭合和开放构象，这是理解自抑制机制的关键。然而，RhoG 介导的 DOCK/ELMO 复合物激活的结构细节仍然难以捉摸。在此，我们展示了 DOCK5/ELMO1 单独以及与 RhoG 和 Rac1 复合的冷冻电镜结构。 DOCK5/ELMO1 结构表现出与 DOCK2/ELMO1 相似的闭合构象，表明 DOCK-A/B 亚家族 (DOCK1−5) 之间存在共同的自抑制状态调节机制。相反，RhoG/DOCK5/ELMO1/Rac1 复合物采用与 DOCK2/ELMO1/Rac1 复合物不同的开放构象，RhoG 与 ELMO1 和 DOCK5 均结合。 DOCK5 磷脂酰肌醇 (3,4,5)-三磷酸结合位点与 RhoG C 末端脂化位点的对齐表明 RhoG 和 DOCK5/ELMO1 同时结合到质膜。 apo 和 RhoG 结合态的结构比较表明，RhoG 促进 DOCK5/ELMO1 从闭合状态到开放状态的构象变化。生化和表面等离子共振 (SPR) 测定证实 RhoG 增强 DOCK5/ELMO1 的 Rac GEF 活性并增加其与 Rac1 的结合亲和力。对结构变异性的进一步分析强调了 DOCK5/ELMO1/Rac1 复合物核心的构象灵活性，可能促进 DOCK5 GEF 结构域与质膜的接近。 这些发现阐明了 RhoG 诱导的 DOCK/ELMO 复合物变构激活和膜结合的结构机制。