PDF(Pubmed)
Abstract：
Dynamin assembles as a helical polymer at the neck of budding endocytic vesicles, constricting the underlying membrane as it progresses through the GTPase cycle to sever vesicles from the plasma membrane. Although atomic models of the dynamin helical polymer bound to guanosine triphosphate (GTP) analogs define earlier stages of membrane constriction, there are no atomic models of the assembled state post-GTP hydrolysis. Here, we used cryo-EM methods to determine atomic structures of the dynamin helical polymer assembled on lipid tubules, akin to necks of budding endocytic vesicles, in a guanosine diphosphate (GDP)-bound, super-constricted state. In this state, dynamin is assembled as a 2-start helix with an inner lumen of 3.4 nm, primed for spontaneous fission. Additionally, by cryo-electron tomography, we trapped dynamin helical assemblies within HeLa cells using the GTPase-defective dynamin K44A mutant and observed diverse dynamin helices, demonstrating that dynamin can accommodate a range of assembled complexes in cells that likely precede membrane fission.
摘要：
Dynamin在出芽内吞囊泡的颈部组装成螺旋聚合物，随着其在GTP酶循环中的进展，收缩下层膜，以从质膜上切断囊泡。尽管与三磷酸鸟苷（GTP）类似物结合的动态蛋白螺旋聚合物的原子模型定义了膜收缩的早期阶段，没有组装态GTP水解后的原子模型。这里,我们使用冷冻EM方法来确定组装在脂质小管上的动态蛋白螺旋聚合物的原子结构，类似于出芽内吞囊泡的颈部，在鸟苷二磷酸(GDP)结合中，超收缩状态。在这种状态下,Dynamin被组装为具有3.4nm内腔的2-start螺旋，准备自发裂变。此外,通过低温电子层析成像，我们使用GTPase缺陷的动态蛋白K44A突变体在HeLa细胞内捕获动态蛋白螺旋组装，并观察到不同的动态蛋白螺旋，证明dynamin可以容纳可能先于膜裂变的细胞中的一系列组装复合物。
