GPI-anchor transamidase complex

GO:0042765 · Other · Multiprotein complex · Proposed

A multisubunit membrane protein complex that attaches preassembled glycosylphosphatidylinositol anchors to proteins. [GO:0042765]

Synonyms: GPI transamidase complex; GPIT complex

Part of: endoplasmic reticulum membrane (GO:0005789)

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
Gaa1 subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	GAA1	UNKNOWN	Named constituent of the budding-yeast GPI-anchor transamidase complex. `GO:0042765` GO:0042765 names Gaa1p as a Saccharomyces GPI-anchor transamidase subunit. `DOI:10.1091/mbc.12.10.3295` Primary Saccharomyces biochemical evidence for this GPI-anchor transamidase constituent.
Gpi8 subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	GPI8	UNKNOWN	Named constituent of the budding-yeast GPI-anchor transamidase complex. `GO:0042765` GO:0042765 names Gpi8p as a Saccharomyces GPI-anchor transamidase subunit. `DOI:10.1091/mbc.12.10.3295` Primary Saccharomyces biochemical evidence for this GPI-anchor transamidase constituent.
Gpi16 subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	GPI16	UNKNOWN	Named constituent of the budding-yeast GPI-anchor transamidase complex. `GO:0042765` GO:0042765 names Gpi16p as a Saccharomyces GPI-anchor transamidase subunit. `DOI:10.1091/mbc.12.10.3295` Primary Saccharomyces biochemical evidence for this GPI-anchor transamidase constituent.
Gpi17 subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	GPI17	UNKNOWN	Named constituent of the budding-yeast GPI-anchor transamidase complex. `GO:0042765` GO:0042765 names Gpi17p as a Saccharomyces GPI-anchor transamidase subunit.
Gab1/Cdc91 subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	GAB1, CDC91	UNKNOWN	Named Gab1p/Cdc91p constituent of the budding-yeast GPI-anchor transamidase complex. `GO:0042765` GO:0042765 names Gab1p as a Saccharomyces GPI-anchor transamidase subunit. `DOI:10.1091/mbc.e02-12-0794` Hong et al. 2003 connected Cdc91p/Gab1p with the yeast GPI-anchor transamidase complex as the fifth subunit.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding yeast contains a GPI-anchor transamidase complex with Gaa1p, Gpi8p, Gpi16p, Gpi17p and Gab1p/Cdc91p subunits. [GO:0042765]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Yeast model in which the membrane GPI transamidase complex was biochemically analyzed and Cdc91p/Gab1p was connected to the complex. [DOI:10.1091/mbc.e02-12-0794]

Functions

attachment of GPI anchor to protein GO:0016255 — The GPI-anchor transamidase complex attaches preassembled glycosylphosphatidylinositol anchors to proteins.
- GO:0042765 GO:0042765 defines the complex by its glycosylphosphatidylinositol-anchor transamidase activity.
- GO:0016255 GO:0016255 denotes attachment of GPI anchor to protein.

Mechanism graphs

GPI transamidase attaches GPI anchors (FUNCTION)

The ER-membrane GPI-anchor transamidase complex contains five named yeast subunits and attaches GPI anchors to protein substrates.

Subject	Predicate	Object	Evidence
Gaa1 subunit	assembles into	GPI-anchor transamidase complex	`GO:0042765` GO:0042765 names Gaa1p as a Saccharomyces GPI-anchor transamidase subunit.
Gpi8 subunit	assembles into	GPI-anchor transamidase complex	`GO:0042765` GO:0042765 names Gpi8p as a Saccharomyces GPI-anchor transamidase subunit.
Gpi16 subunit	assembles into	GPI-anchor transamidase complex	`GO:0042765` GO:0042765 names Gpi16p as a Saccharomyces GPI-anchor transamidase subunit.
Gpi17 subunit	assembles into	GPI-anchor transamidase complex	`GO:0042765` GO:0042765 names Gpi17p as a Saccharomyces GPI-anchor transamidase subunit.
Gab1/Cdc91 subunit	assembles into	GPI-anchor transamidase complex	`GO:0042765` GO:0042765 names Gab1p as a Saccharomyces GPI-anchor transamidase subunit. `DOI:10.1091/mbc.e02-12-0794` Hong et al. 2003 connected Cdc91p/Gab1p with GPI transamidase as the fifth subunit.
GPI-anchor transamidase complex	is embedded in	endoplasmic reticulum membrane	`DOI:10.1091/mbc.12.10.3295` Fraering et al. 2001 analyzed the Saccharomyces membrane GPI transamidase complex.
GPI-anchor transamidase complex	supports	attachment of GPI anchor to protein	`GO:0042765` GO:0042765 defines the complex by its glycosylphosphatidylinositol-anchor transamidase activity.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral GPI-anchor transamidase subunit family groundings for the reviewed label-only Gaa1, Gpi8, Gpi16, Gpi17 and Gab1/Cdc91 component rows. GO exactly grounds the GPI-anchor transamidase complex and names the Saccharomyces cerevisiae Gaa1p, Gpi8p, Gpi16p, Gpi17p and Gab1p/Cdc91p subunits; this first record adds reviewed label-only component rows but leaves exact taxon-agnostic family identifiers unset until they are verified.

Evidence

GO:0042765 Gene Ontology cellular-component term for the GPI-anchor transamidase complex.
GO:0032991 Gene Ontology cellular-component parent term for protein-containing complexes.
GO:0005789 Gene Ontology cellular-component term for the endoplasmic reticulum membrane.
GO:0016255 Gene Ontology biological-process term for attachment of GPI anchor to protein.
DOI:10.1091/mbc.12.10.3295 Fraering et al. 2001, The GPI Transamidase Complex of Saccharomyces, Molecular Biology of the Cell.
DOI:10.1091/mbc.e02-12-0794 Hong et al. 2003, Human PIG-U and Yeast Cdc91p Are the Fifth Subunit of GPI Transamidase That Attaches GPI-Anchors to Proteins, Molecular Biology of the Cell.

Curation history

2026-09-18T20:30:09Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-18T20:31:49Z codex · EXPANDED_RECORD — Added GPI-anchor transamidase synonymy, protein-complex parentage, ER-membrane parthood, reviewed label-only Saccharomyces subunits, a GPI-anchor attachment function, DOI/GO evidence, a nonmechanistic GPIT graph, and a subunit-grounding TODO.
2026-09-18T20:32:40Z codex · REFINED_EVIDENCE — Narrowed the Gpi17 component evidence to the exact GO term rather than using the Fraering Saccharomyces complex citation on every subunit row.
2026-09-18T20:57:04Z codex · ADDRESS_REVIEW — Resolved #1191 by adding the GPIT exact synonym and resolved #1190 by carrying the Cdc91 alias on the Gab1 subunit, graph node, edge evidence, and subunit-boundary TODO.

Source: data/structures/other/gpi_anchor_transamidase_complex.yaml