COPI-coated vesicles mediate trafficking within the Golgi apparatus and from the Golgi to the endoplasmic reticulum. The structures of membrane protein coats, including COPI, have been extensively studied with in vitro reconstitution systems using purified components. Previously we have determined a complete structural model of the in vitro reconstituted COPI coat (Dodonova et al., 2017). Here, we applied cryo-focused ion beam milling, cryo-electron tomography and subtomogram averaging to determine the native structure of the COPI coat within vitrified Chlamydomonas reinhardtii cells. The native algal structure resembles the in vitro mammalian structure, but additionally reveals cargo bound beneath β’–COP. We find that all coat components disassemble simultaneously and relatively rapidly after budding. Structural analysis in situ, maintaining Golgi topology, shows that vesicles change their size, membrane thickness, and cargo content as they progress from cis to trans, but the structure of the coat machinery remains constant.

中文翻译：

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细胞内确定的 COPI 涂层结构

COPI 包被的囊泡介导高尔基体内以及从高尔基体到内质网的运输。膜蛋白外壳的结构，包括 COPI，已经通过使用纯化成分的体外重组系统进行了广泛的研究。此前，我们已经确定了体外重组 COPI 涂层的完整结构模型（Dodonova 等，2017）。在这里，我们应用低温聚焦离子束铣削、低温电子断层扫描和亚断层图平均来确定玻璃化莱茵衣藻细胞内 COPI 涂层的天然结构。天然藻类结构类似于体外哺乳动物结构，但另外还揭示了 β'-COP 下的货物。我们发现所有的外套成分在出芽后同时分解并且相对较快。原位结构分析，