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Updated: May 15, 2026

Cryo-EM and Single-Particle Analysis with Scipion
Published on: May 29, 2021
A pseudoatomic model of the COPII cage obtained from cryo-electron microscopy and mass spectrometry
Alex J Noble1, Qian Zhang, Jason O'Donnell
1Department of Physics, Florida State University, Tallahassee, Florida, USA.
Abstract:
COPII vesicles transport proteins from the endoplasmic reticulum to the Golgi apparatus. Previous COPII-cage cryo-EM structures lacked the resolution necessary to determine the residues of Sec13 and Sec31 that mediate assembly and flexibility of the COPII cage. Here we present a 12-Å structure of the human COPII cage, where the tertiary structure of Sec13 and Sec31 is clearly identifiable. We employ this structure and a homology model of the Sec13-Sec31 complex to create a reliable pseudoatomic model of the COPII cage. We combined this model with hydrogen/deuterium-exchange MS analysis to characterize four distinct contact regions at the vertices of the COPII cage. Furthermore, we found that the two-fold symmetry of the Sec31 dimeric region in Sec13-Sec31 is broken upon cage formation and that the resulting hinge is essential to form the proper edge geometry in COPII cages.
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