endoplasmic reticulum

GO:0005783 · Membrane organelle · Membrane bounded organelle · Proposed

The irregular network of unit membranes, visible only by electron microscopy, that occurs in the cytoplasm of many eukaryotic cells. The membranes form a complex meshwork of tubular channels, which are often expanded into slitlike cavities called cisternae. The ER takes two forms, rough (or granular), with ribosomes adhering to the outer surface, and smooth (with no ribosomes attached). [GO:0005783]

Synonyms: ER

Part of: GO:0012505 — endomembrane system (no local record)

Has part: endoplasmic reticulum membrane (GO:0005789); endoplasmic reticulum lumen (GO:0005788); Sec61 translocon complex (GO:0005784)

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

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
endoplasmic reticulum membrane	Lipid	part of	`GO:0005789`			ESSENTIAL	Lipid bilayer that bounds the endoplasmic reticulum and separates its lumen from cytosol. `GO:0005789` GO:0005789 defines the endoplasmic reticulum membrane as the lipid bilayer surrounding the endoplasmic reticulum.
Sec61 translocon complex	Protein complex	part of	`GO:0005784`			UNKNOWN	Conserved ER membrane channel complex that mediates cotranslational and posttranslational protein translocation. `GO:0005784` GO:0005784 defines the Sec61 translocon complex as a core heterotrimeric ER translocon. `DOI:10.1091/mbc.3.2.129` Stirling et al. 1992 isolated yeast sec61 mutants defective in integral membrane protein insertion into the endoplasmic reticulum.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding yeast has an endoplasmic reticulum with Sec61-dependent protein translocation and linked unfolded-protein-response and ERAD pathways. [DOI:10.1016/s0092-8674(00)80835-1]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding-yeast model for Sec61-dependent endoplasmic-reticulum protein translocation. [DOI:10.1091/mbc.3.2.129]

Functions

protein translocation into the endoplasmic reticulum — Sec61 translocon complexes in the ER membrane move nascent and posttranslational substrate proteins across or into the ER membrane.
- GO:0005784 GO:0005784 identifies the Sec61 translocon complex as functioning in cotranslational and posttranslational translocation events.
- DOI:10.1091/mbc.3.2.129 Stirling et al. 1992 analyzed Saccharomyces cerevisiae sec61 mutants with ER protein-insertion defects.
endoplasmic reticulum unfolded protein response GO:0030968 — The ER stress response coordinates ER-associated degradation with expression of endoplasmic-reticulum resident factors.
- DOI:10.1016/s0092-8674(00)80835-1 Travers et al. 2000 combined functional and genomic analyses to connect the yeast unfolded protein response with ER-associated degradation.
ERAD pathway GO:0036503 — Misfolded or unassembled proteins are recognized in the ER and routed to ER-associated degradation quality-control machinery.
- DOI:10.1016/s0092-8674(00)80835-1 Travers et al. 2000 found that ER-associated degradation and the unfolded protein response are functionally coordinated in yeast.

Mechanism graphs

Yeast ER couples protein entry and quality control (FUNCTION)

In budding yeast, the ER membrane surrounds the ER lumen, embeds Sec61 protein-translocation machinery, and provides the compartment where protein biogenesis is coupled to unfolded-protein-response and ERAD quality-control pathways.

Subject	Predicate	Object	Evidence
endoplasmic reticulum membrane	bounds	endoplasmic reticulum lumen	`GO:0005788` GO:0005788 defines the endoplasmic reticulum lumen as the volume enclosed by ER membranes.
endoplasmic reticulum membrane	is part of	endoplasmic reticulum	`GO:0005783` GO:0005783 defines the ER as an irregular network of unit membranes arranged as tubular channels and cisternae.
Sec61 translocon complex	is embedded in	endoplasmic reticulum membrane	`GO:0005784` GO:0005784 identifies Sec61 as an ER translocon complex.
Sec61 translocon complex	supports	protein translocation into the endoplasmic reticulum	`DOI:10.1091/mbc.3.2.129` Stirling et al. 1992 characterized Saccharomyces cerevisiae sec61 alleles defective in ER protein insertion.
endoplasmic reticulum unfolded protein response	coordinates with	ERAD pathway	`DOI:10.1016/s0092-8674(00)80835-1` Travers et al. 2000 showed coordination between the yeast unfolded protein response and ER-associated degradation.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral component groundings for yeast ER unfolded-protein-response and ER-associated-degradation machinery, including luminal chaperone, retrotranslocation, and ubiquitin-ligase cohorts. This first endoplasmic reticulum record grounds the Sec61 translocon complex and ER membrane but does not overclaim exact identifiers for multi-family UPR and ERAD machinery cohorts.

Evidence

GO:0005783 Gene Ontology cellular-component term for the endoplasmic reticulum.
GO:0005789 Gene Ontology cellular-component term for the endoplasmic reticulum membrane.
GO:0005788 Gene Ontology cellular-component term for the endoplasmic reticulum lumen.
DOI:10.1091/mbc.3.2.129 Stirling et al. 1992, 'Protein translocation mutants defective in the insertion of integral membrane proteins into the endoplasmic reticulum', Molecular Biology of the Cell.
DOI:10.1016/s0092-8674(00)80835-1 Travers et al. 2000, 'Functional and genomic analyses reveal an essential coordination between the unfolded protein response and ER-associated degradation', Cell.

Curation history

2026-09-11T17:01:42Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-11T17:02:39Z codex · EXPANDED_RECORD — Added ER parentage, endomembrane parthood, membrane, lumen, and Sec61 translocon parts, exact ER synonymy, a grounded Sec61 component, Saccharomyces scope, protein-translocation and UPR/ERAD functions, a nonmechanistic protein-biogenesis graph, and a quality-control machinery grounding TODO.
2026-09-11T17:06:39Z codex · CANONICALIZED_LABEL — Updated GO:0036503 references to the canonical 'ERAD pathway' label.
2026-09-11T17:11:35Z codex · ADDRESSED_REVIEW_ISSUES — Addressed review issues #524 and #525 by narrowing the Saccharomyces canonical example to the Sec61 citation scope and changing the graph edge from a membrane-bounds-organelle assertion to an ER-membrane-is-part-of-ER assertion.

Source: data/structures/membrane_organelle/endoplasmic_reticulum.yaml