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Elife. 2017 Nov 17;6. pii: e32493. doi: 10.7554/eLife.32493.

The structure of the COPI coat determined within the cell.

Author information

1
Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.
2
Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.
3
Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried, Germany.

Abstract

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.

KEYWORDS:

COPI; Chlamydomonas reinhardtii; biophysics; cell biology; cryo-electron tomography; membrane trafficking; structural biology; subtomogram averaging

PMID:
29148969
PMCID:
PMC5716667
DOI:
10.7554/eLife.32493
[Indexed for MEDLINE]
Free PMC Article

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