Combinatorial multivalent interactions drive cooperative assembly of the COPII coat

J Cell Biol. 2020 Nov 2;219(11):e202007135. doi: 10.1083/jcb.202007135.


Protein secretion is initiated at the endoplasmic reticulum by the COPII coat, which self-assembles to form vesicles. Here, we examine the mechanisms by which a cargo-bound inner coat layer recruits and is organized by an outer scaffolding layer to drive local assembly of a stable structure rigid enough to enforce membrane curvature. An intrinsically disordered region in the outer coat protein, Sec31, drives binding with an inner coat layer via multiple distinct interfaces, including a newly defined charge-based interaction. These interfaces combinatorially reinforce each other, suggesting coat oligomerization is driven by the cumulative effects of multivalent interactions. The Sec31 disordered region could be replaced by evolutionarily distant sequences, suggesting plasticity in the binding interfaces. Such a multimodal assembly platform provides an explanation for how cells build a powerful yet transient scaffold to direct vesicle traffic.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • COP-Coated Vesicles / genetics
  • COP-Coated Vesicles / metabolism*
  • Endoplasmic Reticulum / metabolism*
  • GTPase-Activating Proteins / genetics
  • GTPase-Activating Proteins / metabolism
  • Protein Binding
  • Protein Transport
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / growth & development
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Vesicular Transport Proteins / genetics
  • Vesicular Transport Proteins / metabolism*


  • GTPase-Activating Proteins
  • SEC23 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Vesicular Transport Proteins