Structures of the atlastin GTPase provide insight into homotypic fusion of endoplasmic reticulum membranes
Structures of the atlastin GTPase provide insight into homotypic fusion of endoplasmic reticulum membranes
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atlastin GTPase 的结构提供了对内质网膜同型融合的深入了解
DOI：
10.1073/pnas.1101643108
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发表时间：
2011-03-08
影响因子：
11.1
通讯作者：
Hu, Junjie
中科院分区：
文献类型：
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作者：
Bian, Xin;Klemm, Robin W.;Hu, Junjie
内质网 (ER) 管状网络的生成需要由类似动力的膜结合 GTP 酶 atlastin (ATL) 介导的同型膜融合。在这里，我们确定了人 ATL1 胞质片段的晶体结构，这有助于深入了解膜融合的机制。该结构揭示了一个 GTPase 结构域和一个三螺旋束，通过连接区连接。一种结构对应于融合前状态，其中相邻膜中的 ATL 分子通过其 GTP 酶结构域相互作用，与结合在界面上的核苷酸形成二聚体。另一种结构对应于 GTP 水解和磷酸盐释放后产生的融合后状态。与融合前结构相比，两个 ATL 分子的三螺旋束相对于 GTPase 结构域发生了重大构象变化，从而可以将膜拉在一起。所提出的融合机制得到了野生型和突变型全长果蝇 ATL 的生化实验和融合测定的支持。这些实验还表明，两个跨膜片段后面的 C 端胞质尾部促进了膜融合。最后，我们的结果表明，导致遗传性痉挛性截瘫的 ATL1 突变会损害同型 ER 融合。
The generation of the tubular network of the endoplasmic reticulum (ER) requires homotypic membrane fusion that is mediated by the dynamin- like, membrane-bound GTPase atlastin (ATL). Here, we have determined crystal structures of the cytosolic segment of human ATL1, which give insight into the mechanism of membrane fusion. The structures reveal a GTPase domain and athree-helix bundle, connected by a linker region. One structure corresponds to a prefusion state, in which ATL molecules in apposing membranes interact through their GTPase domains to form a dimer with the nucleotides bound at the interface. The other structure corresponds to a postfusion state generated after GTP hydrolysis and phosphate release. Compared with the prefusion structure, the three-helix bundles of the two ATL molecules undergo a major conformational change relative to the GTPase domains, which could pull the membranes together. The proposed fusion mechanism is supported by biochemical experiments and fusion assays with wild-type and mutant full-length Drosophila ATL. These experiments also show that membrane fusion is facilitated by the C-terminal cytosolic tails following the two transmembrane segments. Finally, our results show that mutations in ATL1 causing hereditary spastic paraplegia compromise homotypic ER fusion.