TRAPPI protein complex

GO:1990070 · Other · Multiprotein complex · Proposed

A complex that tethers COPII vesicles at ER-Golgi intermediate compartment. Its role in this part of the vesicular transport may start at the ER exit sites. Binds to a component of the COPII coat. In yeast it includes the following subunits: Bet3 (as homodimer), Bet5, Trs20, Trs23, Trs31, Trs33 which are regarded as the core subunits of all TRAPP complexes in yeast. [GO:1990070]

Synonyms: TRAPP core complex; TRAPP I; TRAPP I complex

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
Bet3 TRAPPI subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	BET3	UNKNOWN	Core TRAPPI constituent present as the homodimeric Bet3 subunit class in the yeast TRAPP core complex. `GO:1990070` GO:1990070 names Bet3 as a homodimeric yeast TRAPPI core subunit. `DOI:10.1078/S0171-9335(04)70009-6` Sacher et al. 2000 noted that Bet3 had been described previously as a TRAPP subunit. `DOI:10.1016/j.cell.2006.09.029` Kim et al. 2006 resolved the architecture of the seven-chain yeast TRAPP I vesicle-tethering factor.
Bet5 TRAPPI subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	BET5	UNKNOWN	Core constituent of the yeast TRAPPI vesicle-tethering complex. `GO:1990070` GO:1990070 names Bet5 as a yeast TRAPPI core subunit. `DOI:10.1078/S0171-9335(04)70009-6` Sacher et al. 2000 noted that Bet5 had been described previously as a TRAPP subunit. `DOI:10.1016/j.cell.2006.09.029` Kim et al. 2006 resolved the architecture of the seven-chain yeast TRAPP I vesicle-tethering factor.
Trs20 TRAPPI subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	TRS20	UNKNOWN	Core constituent of the yeast TRAPPI vesicle-tethering complex. `GO:1990070` GO:1990070 names Trs20 as a yeast TRAPPI core subunit. `DOI:10.1078/S0171-9335(04)70009-6` Sacher et al. 2000 noted that Trs20 had been described previously as a TRAPP subunit. `DOI:10.1016/j.cell.2006.09.029` Kim et al. 2006 resolved the architecture of the seven-chain yeast TRAPP I vesicle-tethering factor.
Trs23 TRAPPI subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	TRS23	UNKNOWN	Core constituent of the yeast TRAPPI vesicle-tethering complex. `GO:1990070` GO:1990070 names Trs23 as a yeast TRAPPI core subunit. `DOI:10.1078/S0171-9335(04)70009-6` Sacher et al. 2000 noted that Trs23 had been described previously as a TRAPP subunit. `DOI:10.1016/j.cell.2006.09.029` Kim et al. 2006 resolved the architecture of the seven-chain yeast TRAPP I vesicle-tethering factor.
Trs31 TRAPPI subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	TRS31	UNKNOWN	Core constituent of the yeast TRAPPI vesicle-tethering complex. `GO:1990070` GO:1990070 names Trs31 as a yeast TRAPPI core subunit. `DOI:10.1078/S0171-9335(04)70009-6` Sacher et al. 2000 identified Trs31 among the additional yeast TRAPP subunits. `DOI:10.1016/j.cell.2006.09.029` Kim et al. 2006 resolved the architecture of the seven-chain yeast TRAPP I vesicle-tethering factor.
Trs33 TRAPPI subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	TRS33	UNKNOWN	Core constituent of the yeast TRAPPI vesicle-tethering complex. `GO:1990070` GO:1990070 names Trs33 as a yeast TRAPPI core subunit. `DOI:10.1078/S0171-9335(04)70009-6` Sacher et al. 2000 noted that Trs33 had been described previously as a TRAPP subunit. `DOI:10.1016/j.cell.2006.09.029` Kim et al. 2006 resolved the architecture of the seven-chain yeast TRAPP I vesicle-tethering factor.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding yeast has a TRAPPI complex that tethers COPII vesicles during endoplasmic-reticulum-to-Golgi traffic. [DOI:10.1016/s1097-2765(01)00190-3]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding-yeast model in which purified TRAPP I was shown to tether COPII vesicles specifically in vitro. [DOI:10.1016/s1097-2765(01)00190-3]

Functions

endoplasmic reticulum to Golgi vesicle-mediated transport GO:0006888 — TRAPPI tethers COPII vesicles at the ER-Golgi interface during anterograde vesicle-mediated transport toward the Golgi.
- GO:0006888 GO:0006888 denotes COPII-vesicle-mediated transport from the endoplasmic reticulum to the Golgi.
- DOI:10.1016/s1097-2765(01)00190-3 Sacher et al. 2001 reconstituted COPII vesicle targeting with purified TRAPP I.

Mechanism graphs

TRAPPI supports yeast ER-to-Golgi vesicle tethering (FUNCTION)

In Saccharomyces cerevisiae, Bet3, Bet5, Trs20, Trs23, Trs31 and Trs33 form the TRAPPI core complex that specifically tethers COPII vesicles during ER-to-Golgi traffic.

Subject	Predicate	Object	Evidence
Bet3 TRAPPI subunit	is part of	TRAPPI protein complex	`GO:1990070` GO:1990070 names Bet3 as a yeast TRAPPI core subunit. `DOI:10.1078/S0171-9335(04)70009-6` Sacher et al. 2000 placed Bet3, Bet5, Trs20, Trs23, Trs31 and Trs33 among yeast TRAPP subunits. `DOI:10.1016/j.cell.2006.09.029` Kim et al. 2006 resolved the architecture of the yeast TRAPP I complex.
Bet5 TRAPPI subunit	is part of	TRAPPI protein complex	`GO:1990070` GO:1990070 names Bet5 as a yeast TRAPPI core subunit. `DOI:10.1078/S0171-9335(04)70009-6` Sacher et al. 2000 placed Bet3, Bet5, Trs20, Trs23, Trs31 and Trs33 among yeast TRAPP subunits. `DOI:10.1016/j.cell.2006.09.029` Kim et al. 2006 resolved the architecture of the yeast TRAPP I complex.
Trs20 TRAPPI subunit	is part of	TRAPPI protein complex	`GO:1990070` GO:1990070 names Trs20 as a yeast TRAPPI core subunit. `DOI:10.1078/S0171-9335(04)70009-6` Sacher et al. 2000 placed Bet3, Bet5, Trs20, Trs23, Trs31 and Trs33 among yeast TRAPP subunits. `DOI:10.1016/j.cell.2006.09.029` Kim et al. 2006 resolved the architecture of the yeast TRAPP I complex.
Trs23 TRAPPI subunit	is part of	TRAPPI protein complex	`GO:1990070` GO:1990070 names Trs23 as a yeast TRAPPI core subunit. `DOI:10.1078/S0171-9335(04)70009-6` Sacher et al. 2000 placed Bet3, Bet5, Trs20, Trs23, Trs31 and Trs33 among yeast TRAPP subunits. `DOI:10.1016/j.cell.2006.09.029` Kim et al. 2006 resolved the architecture of the yeast TRAPP I complex.
Trs31 TRAPPI subunit	is part of	TRAPPI protein complex	`GO:1990070` GO:1990070 names Trs31 as a yeast TRAPPI core subunit. `DOI:10.1078/S0171-9335(04)70009-6` Sacher et al. 2000 placed Bet3, Bet5, Trs20, Trs23, Trs31 and Trs33 among yeast TRAPP subunits. `DOI:10.1016/j.cell.2006.09.029` Kim et al. 2006 resolved the architecture of the yeast TRAPP I complex.
Trs33 TRAPPI subunit	is part of	TRAPPI protein complex	`GO:1990070` GO:1990070 names Trs33 as a yeast TRAPPI core subunit. `DOI:10.1078/S0171-9335(04)70009-6` Sacher et al. 2000 placed Bet3, Bet5, Trs20, Trs23, Trs31 and Trs33 among yeast TRAPP subunits. `DOI:10.1016/j.cell.2006.09.029` Kim et al. 2006 resolved the architecture of the yeast TRAPP I complex.
TRAPPI protein complex	participates in	endoplasmic reticulum to Golgi vesicle-mediated transport	`DOI:10.1016/s1097-2765(01)00190-3` Sacher et al. 2001 used chemically pure TRAPP I and COPII vesicles to reconstitute specific vesicle targeting.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral family groundings for the six yeast TRAPPI core subunits. This first TRAPPI record names the yeast Bet3, Bet5, Trs20, Trs23, Trs31 and Trs33 constituent subunits but leaves InterPro, Pfam, or Complex Portal grounding unset until exact orthology and paralogy boundaries are reviewed per subunit.
CURATION_TODO (RESOLVED): Do not model Tca17, Trs65, Trs85, Trs120 or Trs130 as constituent TRAPPI core-complex components. GO:0030008 is the broader TRAPP-complex parent, whereas GO:1990070 denotes the TRAPPI core complex. Tca17, Trs65, Trs120 and Trs130 are TRAPPII-specific subunits in the GO definition of GO:1990071; Trs85 is the defining extra yeast TRAPPIII subunit in GO:1990072.

Evidence

GO:1990070 Gene Ontology cellular-component term for the TRAPPI protein complex.
GO:0030008 Gene Ontology cellular-component parent term for TRAPP complexes.
GO:0006888 Gene Ontology biological-process term for endoplasmic-reticulum-to-Golgi vesicle-mediated transport.
DOI:10.1093/emboj/17.9.2494 Sacher et al. 1998, TRAPP, a highly conserved novel complex on the cis-Golgi that mediates vesicle docking and fusion, EMBO Journal.
DOI:10.1078/S0171-9335(04)70009-6 Sacher et al. 2000, Identification and characterization of five new subunits of TRAPP, European Journal of Cell Biology.
DOI:10.1016/s1097-2765(01)00190-3 Sacher et al. 2001, TRAPP I implicated in the specificity of tethering in ER-to-Golgi transport, Molecular Cell.
DOI:10.1016/j.cell.2006.09.029 Kim et al. 2006, The architecture of the multisubunit TRAPP I complex suggests a model for vesicle tethering, Cell.

Curation history

2026-09-16T19:54:49Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-16T19:56:34Z codex · EXPANDED_RECORD — Added TRAPPI synonymy, TRAPP parentage, reviewed-label-only Bet3/Bet5/Trs20/Trs23/Trs31/Trs33 yeast components, Saccharomyces cerevisiae scope, an ER-to-Golgi vesicle transport function, GO/DOI evidence, a nonmechanistic yeast TRAPPI tethering graph, a subunit-grounding TODO, and a resolved boundary for TRAPPII/TRAPPIII-specific subunits.
2026-09-16T19:57:05Z codex · REFINED_RECORD — Made the resolved TRAPPI subtype-boundary discussion also exclude Tca17, which GO:1990071 treats as a TRAPPII-specific yeast subunit.
2026-09-16T20:06:32Z codex · FIXED_VALIDATION_DEFECT — Replaced the broad components discussion anchor with explicit TRAPPI component anchors so corpus-integrity checks can resolve every attaches_to target.
2026-09-16T20:18:21Z codex · ADDRESSED_PR_REVIEW — Resolved PR #1124 issue #1125 by adding Sacher et al. 2000 primary subunit-identification evidence to the six TRAPPI component rows and their yeast graph parthood edges.

Source: data/structures/other/trappi_protein_complex.yaml