Structure of the Sec13/31 COPII coat cage
Structure of the Sec13/31 COPII coat cage
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DOI：
10.1038/nature04339
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发表时间：
2006-01-12
期刊：
影响因子：
64.8
通讯作者：
Balch, WE
中科院分区：
文献类型：
--
作者：
Stagg, SM;Gürkan, C;Balch, WE
真核细胞的内膜是一种动态的结构，通过特殊的细胞器(1)的活动，如外壳蛋白复合体II(COPII)，它介导内质网(ER)(2，3)的货物输出。COPII由Sar1 GTPase、Sec23和SEC24(Sec23/24)和Sec13和Sec31(Sec13/31)组成，其中Sec23是Sar1特异性GTPase激活蛋白，SEC24在货物选择中起作用(3)。最近的结果表明，Sec23/24和Sec13/31可以自组装形成COPII笼状颗粒(4)，现在我们证明了在没有Sec23/24的情况下，Sec13/31可以自组装成最小的笼子。我们用低温电子显微镜和单粒子分析对这些Sec13/31笼进行了30埃分辨率的三维重建。这些结果揭示了一种新的立方八面体几何结构，具有形成灵活晶格和产生各种容器的潜力。我们的数据与COPII涂层复合体组装模型一致，在该模型中，Sec23/24作为多价配体的非结构角色定位了Sec13/31的自组装，形成了驱动ER货物输出的笼状晶格。
Endomembranes of eukaryotic cells are dynamic structures that are in continuous communication through the activity of specialized cellular machineries(1), such as the coat protein complex II ( COPII), which mediates cargo export from the endoplasmic reticulum (ER)(2,3). COPII consists of the Sar1 GTPase, Sec23 and Sec24 (Sec23/24), where Sec23 is a Sar1-specific GTPase-activating protein and Sec24 functions in cargo selection, and Sec13 and Sec31 (Sec13/31), which has a structural role(3). Whereas recent results have shown that Sec23/24 and Sec13/31 can self-assemble to form COPII cage-like particles(4), we now show that Sec13/31 can self-assemble to form minimal cages in the absence of Sec23/24. We present a three-dimensional reconstruction of these Sec13/31 cages at 30 angstrom resolution using cryo-electron microscopy and single particle analysis. These results reveal a novel cuboctahedron geometry with the potential to form a flexible lattice and to generate a diverse range of containers. Our data are consistent with a model for COPII coat complex assembly in which Sec23/24 has a non-structural role as a multivalent ligand localizing the self-assembly of Sec13/31 to form a cage lattice driving ER cargo export.