囊泡运输是真核细胞特有的物质运输方式，对维持细胞稳态至关重要。包被蛋白是参与囊泡运输的中心机器，它可以正确识别货物分子，并诱导细胞膜变形形成囊泡。小G蛋白Arf负责将包被蛋白从溶液中招募到细胞膜上组装形成复合体。COPI小泡介导从顺面高尔基体网状区到内质网及高尔基体囊膜内部之间的物质运输。在被Arf1招募到高尔基体膜上之前，COPI小泡的包被复合物在溶液中预组装为一个异源七聚体，即包被蛋白复合物coatomer。虽然COPI在膜上三维结构已经解析，但由于其在溶液中的构象多变，其三维结构一直无法解析；如何从溶液中的构象转变为膜上包被中的构象，其机制并不清楚。本项目拟利用冷冻电镜单颗粒技术和冷冻电子断层技术，研究包被蛋白复合物在溶液状态、膜结合状态的三维结构、骨架亚复合物和接头亚复合物的高分辨率结构、以及其与货物分子和调节因子Arf1、ArfGAP1的相互作用，阐明COPI小形成的分制。

Eukaryotic cells exchange material between cellular compartments by vesicle trafficking, which is responsible for cellular homeostasis. The formation of these vesicles is initiated by recruiting cytosolic coat proteins to donor membrane and their following assembly into cargo-structure. COPI-coated vesicles play major roles in sorting cargoes from cis-Golgi network back to endoplasmic reticulum or within Golgi Eukaryotic cells exchange material between cellular compartments by vesicle trafficking, which is responsible for cellular homeostasis. Coat proteins play a key role in intracellular transport as core machines, with two major functions, binding to cargoes for the proper packaging and bending membrane that generates transport vesicles. The ADP-ribosylation factor (ARF) family of small GTPases has been shown to regulate these function of coat proteins by dictating their recruitment from the cytosol to membrane. COPI-coated vesicles play major roles in sorting cargoes from cis-Golgi network (CGN) back to endoplasmic reticulum (ER) or within Golgi apparatus. Before recruitment by Arf1，coat proteins for COPI are pre-assembled as a single soluble protein complex in the cytoplasm, termed coatomer. The structure of membrane bound coatomer in COPI coats is reported，however the substantial conformational flexibility of cytoplasmic coatomer hinders in depth understandings of its three dimensional structural details. And the mechanism of how coatomer changes its conformation from cytosolic state to membrane state remains unclear. Here，we aim to study three dimensional structures of coatmer in cytosolic state and membrane bound state, scaffold subcomplex and adaptor subcomplex, and their interactions with cargo, Arf1 and ArfGAP1, to investigate the conformational transition of coatomer and functional mechanism in the formation of COPI vesicle.