AP-1 adaptor complex
A heterotetrameric AP-type membrane coat adaptor complex that consists of beta1, gamma, mu1 and sigma1 subunits and links clathrin to the membrane surface of a vesicle; vesicles with AP-1-containing coats are normally found primarily in the trans-Golgi network. In at least humans, the AP-1 complex can be heterogeneric due to the existence of multiple subunit isoforms encoded by different genes (gamma1 and gamma2, mu1A and mu1B, and sigma1A, sigma1B and sigma1C). [GO:0030121]
Part of: clathrin coat of trans-Golgi network vesicle (GO:0030130)
Components
| Component | Type | Part of / acts on | Grounding | Genes | Stoichiometry | Essential | Role |
|---|---|---|---|---|---|---|---|
| AP-1 beta1 subunit | Protein | part of | Reviewed label only (reviewed name; no accession asserted) | UNKNOWN | Large beta1 subunit of the heterotetrameric AP-1 adaptor complex.
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| AP-1 gamma subunit | Protein | part of | Reviewed label only (reviewed name; no accession asserted) | UNKNOWN | Large gamma subunit of the heterotetrameric AP-1 adaptor complex.
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| AP-1 mu1 subunit | Protein | part of | Reviewed label only (reviewed name; no accession asserted) | UNKNOWN | Medium mu1 subunit of the heterotetrameric AP-1 adaptor complex.
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| AP-1 sigma1 subunit | Protein | part of | Reviewed label only (reviewed name; no accession asserted) | UNKNOWN | Small sigma1 subunit of the heterotetrameric AP-1 adaptor complex.
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Taxonomic distribution
NCBITaxon:4932Saccharomyces cerevisiae — COMMON: Saccharomyces cerevisiae has an AP-1 clathrin adaptor complex whose subunit composition was defined by coimmunoprecipitation. [DOI:10.1091/mbc.10.11.3643]
Canonical examples
NCBITaxon:4932Saccharomyces cerevisiae — Budding-yeast model in which AP-1 was biochemically assigned as a clathrin-interacting adaptor complex. [DOI:10.1091/mbc.10.11.3643]
Functions
- AP-1-dependent late-Golgi cargo sorting — Yeast AP-1 contributes to clathrin-associated sorting of late Golgi and Golgi/early-endosome cargoes.
DOI:10.1016/S1534-5807(02)00127-2Valdivia et al. 2002 connect the yeast clathrin adaptor protein complex 1 to efficient retention of a subset of late Golgi membrane proteins.DOI:10.1091/mbc.e15-09-0621Whitfield et al. 2016 show that budding yeast has two AP-1 forms with alternate mu chains that confer distinct cargo-sorting functions.
Mechanism graphs
Beta1, gamma, mu1 and sigma1 subunits form AP-1 (FUNCTION)
The AP-1 adaptor complex is a clathrin adaptor and heterotetrameric component of the trans-Golgi network vesicle clathrin coat.
| Subject | Predicate | Object | Evidence |
|---|---|---|---|
| AP-1 beta1 subunit | is part of | AP-1 adaptor complex |
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| AP-1 gamma subunit | is part of | AP-1 adaptor complex |
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| AP-1 mu1 subunit | is part of | AP-1 adaptor complex |
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| AP-1 sigma1 subunit | is part of | AP-1 adaptor complex |
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| AP-1 adaptor complex | is part of | clathrin coat of trans-Golgi network vesicle |
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| AP-1 adaptor complex | supports | late Golgi cargo sorting |
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Discussions
- INTERPRETATION (RESOLVED): Represent AP-1 as a TGN coat adaptor, not as the complete TGN clathrin coat. GO:0030121 is a subtype of GO:0030131 clathrin adaptor complex and part of GO:0030130 clathrin coat of trans-Golgi network vesicle. This record therefore represents the AP-1 adaptor heterotetramer and links it to the containing TGN clathrin coat through part_of.
- INTERPRETATION (RESOLVED): Exclude Mil1 from core AP-1 subunits. Whitfield et al. 2016 identify Mil1 as a conserved regulatory protein that binds the Apm2 alternate mu subunit and contributes to membrane recruitment. That supports a regulatory interaction, not stable beta1/gamma/mu1/sigma1 membership in the core AP-1 heterotetramer.
- CURATION_TODO (OPEN): Resolve exact source-neutral groundings for the AP-1 beta1, gamma, mu1 and sigma1 subunit classes. GO gives the exact AP-1 complex identity and names its subunit classes, but exact source-neutral InterPro, Pfam or NCBIfam CURIEs for those AP-1-specific classes were not curated in this pass.
Evidence
GO:0030121Gene Ontology cellular-component term for the AP-1 adaptor complex.GO:0030131Gene Ontology cellular-component parent term for clathrin adaptor complexes.GO:0030130Gene Ontology cellular-component term for the containing clathrin coat of trans-Golgi network vesicle.DOI:10.1091/mbc.10.11.3643Yeung, Phan and Payne 1999, Adaptor Complex-independent Clathrin Function in Yeast, Molecular Biology of the Cell.DOI:10.1016/S1534-5807(02)00127-2Valdivia, Baggott, Chuang and Schekman 2002, The Yeast Clathrin Adaptor Protein Complex 1 Is Required for the Efficient Retention of a Subset of Late Golgi Membrane Proteins, Developmental Cell.DOI:10.1091/mbc.e15-09-0621Whitfield et al. 2016, The alternate AP-1 adaptor subunit Apm2 interacts with the Mil1 regulatory protein and confers differential cargo sorting, Molecular Biology of the Cell.
Curation history
2026-09-16T12:52:22Zcodex · CREATED_RECORD — Scaffolded by scripts/new_record.py2026-09-16T12:53:09Zcodex · EXPANDED_RECORD — Added clathrin-adaptor parentage, TGN clathrin-coat parthood, reviewed-label-only beta1/gamma/mu1/sigma1 subunits, Saccharomyces AP-1 distribution and function evidence, GO/DOI evidence, a nonmechanistic AP-1 topology graph, and TGN-coat, Mil1-boundary and subunit-grounding discussions.2026-09-16T12:59:31Zcodex · CURATED_DISCUSSION_ANCHORS — Retargeted the Mil1 boundary discussion from the components section to the four AP-1 core subunit anchors2026-09-16T13:06:00Zcodex · ADDRESSED_PR_REVIEW — Narrowed the AP-1 canonical example note to the Yeung-supported budding-yeast AP-1 assignment; addresses PR #1096 review issue #1097.