COPII vesicle coat

GO:0030127 · Other · Multiprotein complex · Proposed

A COPII coat protein complex that assembles on endoplasmic-reticulum membranes to bud COPII-coated ER-to-Golgi transport vesicles; in budding yeast it contains Sar1p, Sec23p, Sec24p, Sec13p, and Sec31p. [GO:0030127]

Part of: COPII-coated ER to Golgi transport vesicle (GO:0030134)

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Essential	Role
Sar1-family COPII GTPase	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	SAR1	UNKNOWN	Small GTPase COPII coat constituent that initiates inner-coat recruitment to endoplasmic-reticulum membranes. `GO:0030127` GO:0030127 names Sar1p among the Saccharomyces cerevisiae COPII vesicle coat subunits. `PMID:8004676` Barlowe et al. 1994 identified Sar1p with Sec13p, Sec31p, Sec23p, and Sec24p as Sec proteins that form the COPII coat driving ER vesicle budding.
Sec23/Sec24 inner COPII coat	Protein complex	part of	Reviewed label only (reviewed name; no accession asserted)	SEC23, SEC24	UNKNOWN	Inner COPII coat subcomplex that links cargo and the ER membrane to the outer Sec13/Sec31 cage. `GO:0030134` GO:0030134 describes the COPII coat complex as formed by Sec23p/Sec24p and Sec13p/Sec31p heterodimers. `DOI:10.7554/elife.00951` Zanetti et al. 2013 resolved a membrane-assembled COPII coat and distinguish inner coat proteins from outer COPII cage components.
Sec13/Sec31 outer COPII coat	Protein complex	part of	Reviewed label only (reviewed name; no accession asserted)	SEC13, SEC31	UNKNOWN	Outer COPII coat subcomplex that polymerizes into a cage around the inner coat on nascent ER-derived vesicles. `GO:0030134` GO:0030134 describes the COPII coat complex as formed by Sec23p/Sec24p and Sec13p/Sec31p heterodimers. `DOI:10.7554/elife.00951` Zanetti et al. 2013 used cryo-electron tomography to analyze the complete membrane-assembled COPII coat and its outer-coat arrangement.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding yeast has a COPII vesicle coat built from Sar1p, Sec23p, Sec24p, Sec13p, and Sec31p that buds transport vesicles from the endoplasmic reticulum. [PMID:8004676]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding-yeast model in which Sar1p, Sec13p, Sec31p, Sec23p, and Sec24p were identified as the COPII coat driving ER transport-vesicle budding. [PMID:8004676]

Functions

COPII-coated vesicle budding GO:0090114 — The COPII vesicle coat forms on ER membranes during evagination of a COPII-coated vesicle.
- GO:0090114 GO:0090114 denotes the COPII-coated vesicle budding process that evaginates ER membrane into a COPII-coated vesicle.
- PMID:9568718 Matsuoka et al. 1998 reconstituted COPII-coated vesicle formation with purified coat proteins and chemically defined liposomes.

Mechanism graphs

COPII subcomplexes assemble a yeast ER vesicle coat (ASSEMBLY)

In Saccharomyces cerevisiae, Sar1p, the Sec23/Sec24 inner coat, and the Sec13/Sec31 outer coat assemble at ER membranes into the COPII vesicle coat that buds COPII-coated ER-to-Golgi transport vesicles.

Subject	Predicate	Object	Evidence
Sar1-family COPII GTPase	is recruited to	endoplasmic reticulum membrane	`PMID:8004676` Barlowe et al. 1994 identified Sar1p as a COPII Sec protein that drives vesicle budding from the ER.
Sar1-family COPII GTPase	recruits	Sec23/Sec24 inner COPII coat	`PMID:9568718` Matsuoka et al. 1998 reconstituted vesicle formation with purified COPII coat proteins.
Sec23/Sec24 inner COPII coat	links to	Sec13/Sec31 outer COPII coat	`DOI:10.7554/elife.00951` Zanetti et al. 2013 distinguish inner COPII proteins from outer COPII components in the complete assembled coat.
Sar1-family COPII GTPase	is part of	COPII vesicle coat	`GO:0030127` GO:0030127 includes Sar1p among the yeast COPII subunits.
Sec23/Sec24 inner COPII coat	is part of	COPII vesicle coat	`GO:0030134` GO:0030134 describes the COPII coat complex as formed by Sec23p/Sec24p heterodimers.
Sec13/Sec31 outer COPII coat	is part of	COPII vesicle coat	`GO:0030134` GO:0030134 describes the COPII coat complex as formed by Sec13p/Sec31p heterodimers.
COPII vesicle coat	assembles on	endoplasmic reticulum membrane	`GO:0090114` GO:0090114 defines COPII-coated vesicle budding as evagination of an endoplasmic reticulum membrane to form a COPII-coated vesicle. `PMID:9568718` Matsuoka et al. 1998 reconstituted COPII-coated vesicle formation with purified coat proteins and chemically defined liposomes.
COPII vesicle coat	is part of	COPII-coated ER to Golgi transport vesicle	`GO:0030134` GO:0030134 defines the COPII-coated ER to Golgi transport vesicle by its COPII coat.
COPII vesicle coat	participates in	COPII-coated vesicle budding	`GO:0090114` GO:0090114 defines COPII-coated vesicle budding as evagination of ER membrane to form a COPII-coated vesicle.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral family or complex groundings for Sar1 and the Sec23/Sec24 and Sec13/Sec31 COPII coat subcomplexes. This first COPII record names the experimentally defined Saccharomyces coat constituents, while leaving InterPro, Pfam, GO, or Complex Portal grounding unset until exact source-neutral family and subcomplex boundaries are reviewed.

Evidence

GO:0030127 Gene Ontology cellular-component term for the COPII vesicle coat.
GO:0030120 Gene Ontology cellular-component parent for vesicle coats.
GO:0030134 Gene Ontology cellular-component term for the COPII-coated ER to Golgi transport vesicle that carries the COPII coat.
GO:0090114 Gene Ontology biological-process term for COPII-coated vesicle budding.
PMID:8004676 Barlowe et al. 1994, 'COPII: A membrane coat formed by Sec proteins that drive vesicle budding from the endoplasmic reticulum', Cell.
PMID:9568718 Matsuoka et al. 1998, 'COPII-Coated Vesicle Formation Reconstituted with Purified Coat Proteins and Chemically Defined Liposomes', Cell.
DOI:10.7554/elife.00951 Zanetti et al. 2013, 'The structure of the COPII transport-vesicle coat assembled on membranes', eLife.

Curation history

2026-09-12T07:23:05Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-12T07:23:57Z codex · EXPANDED_RECORD — Added vesicle-coat parentage, COPII-coated vesicle parthood, reviewed-label-only Sar1, Sec23/Sec24, and Sec13/Sec31 components, Saccharomyces scope, a COPII budding function, DOI/GO evidence, a nonmechanistic coat-assembly graph, and a subcomplex-grounding TODO.
2026-09-12T07:28:55Z codex · ADDRESS_REVIEW — Addressed PR #605 review issues #606 and #607 by weakening the Sec23/Sec24-to-Sec13/Sec31 edge from directional recruitment to linkage in the assembled coat and by adding an edge from the complete COPII coat to the ER membrane.
2026-09-21T09:25:14Z codex · REPLACED_UNREADABLE_EVIDENCE — Resolved #1229 by routing Barlowe et al. 1994 COPII evidence through reachable PMID:8004676 instead of the unreadable Cell DOI.
2026-09-21T11:34:06Z codex · REPLACED_UNREADABLE_EVIDENCE — Resolved #1237 by routing Matsuoka et al. 1998 COPII liposome evidence through reachable PMID:9568718 instead of the unreadable Cell DOI.

Source: data/structures/other/copii_vesicle_coat.yaml