The structure of the COPI coat determined within the cell

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

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • COP-Coated Vesicles / chemistry
  • Chlamydomonas reinhardtii / chemistry*
  • Coat Protein Complex I / chemistry*
  • Cryoelectron Microscopy
  • Electron Microscope Tomography
  • Models, Molecular
  • Protein Conformation

Substances

  • Coat Protein Complex I