9Å structure of the COPI coat reveals that the Arf1 GTPase occupies two contrasting molecular environments
9Å structure of the COPI coat reveals that the Arf1 GTPase occupies two contrasting molecular environments
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DOI：
10.7554/elife.26691
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发表时间：
2017-06-16
期刊：
影响因子：
7.7
通讯作者：
Briggs, John A. G.
中科院分区：
文献类型：
--
作者：
Dodonova, Svetlana O.;Aderhold, Patrick;Briggs, John A. G.
在高尔基体内以及高尔基体和内质网之间，COPI包被的囊泡起到调节转运的作用。COPI包被囊泡的组装是由小的GTPase Arf1启动的，它将辅酶复合体招募到膜上，触发聚合和萌发。囊泡在与靶膜融合之前脱壳。外壳组分在COPI和笼状蛋白/接头蛋白之间结构保守。利用低温电子断层扫描和亚断层图像平均，我们以9埃的分辨率确定了体外组装在膜上的CoPI涂层的结构。我们还得到了β-CoP的2.57埃分辨晶体结构。通过组合这些结构，我们建立了涂层的分子模型。我们还在调节毛皮解离的ArfGAP蛋白存在的情况下确定了毛皮结构。我们发现Arf1在被膜内占据了截然不同的分子环境，这导致我们假设一些Arf1分子可能调控囊泡组装，而另一些分子可能调控被膜的解体。
COPI coated vesicles mediate trafficking within the Golgi apparatus and between the Golgi and the endoplasmic reticulum. Assembly of a COPI coated vesicle is initiated by the small GTPase Arf1 that recruits the coatomer complex to the membrane, triggering polymerization and budding. The vesicle uncoats before fusion with a target membrane. Coat components are structurally conserved between COPI and clathrin/adaptor proteins. Using cryo-electron tomography and subtomogram averaging, we determined the structure of the COPI coat assembled on membranes in vitro at 9 angstrom resolution. We also obtained a 2.57 angstrom resolution crystal structure of beta delta-COP. By combining these structures we built a molecular model of the coat. We additionally determined the coat structure in the presence of ArfGAP proteins that regulate coat dissociation. We found that Arf1 occupies contrasting molecular environments within the coat, leading us to hypothesize that some Arf1 molecules may regulate vesicle assembly while others regulate coat disassembly.