Sec61 translocon complex

GO:0005784 · Other · Multiprotein complex · Proposed

A heterotrimeric endoplasmic-reticulum membrane translocon that forms a protein-conducting channel for co- and post-translational substrate movement across or into the ER membrane. [GO:0005784]

Synonyms: Sec61 complex; ER Sec61 translocon

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
Sec61 alpha protein-conducting channel subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	SEC61	ESSENTIAL	Multi-pass ER membrane subunit that forms the protein-conducting pore and lateral gate of the Sec61 translocon. `GO:0005784` GO:0005784 defines the Sec61 translocon as a heterotrimer whose alpha subunit forms the core protein-conducting channel. `DOI:10.1091/mbc.3.2.129` Stirling et al. 1992 cloned Saccharomyces SEC61 and found that Sec61p is an integral ER membrane protein required for secretory and membrane-polypeptide insertion.
Sec61 beta subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	SBH1	UNKNOWN	Small tail-anchored beta subunit, represented in Saccharomyces by Sbh1p, that associates with the Sec61 alpha and gamma subunits. `DOI:10.1038/367654a0` Hartmann et al. 1994 identified yeast Sbh1p as a conserved component of the eukaryotic protein-translocation complex. `DOI:10.1074/jbc.M701840200` Feng et al. 2007 showed that the Sbh1p transmembrane domain is sufficient for coimmunoprecipitation with Sec61p and Sss1p.
Sec61 gamma subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	SSS1	ESSENTIAL	Small conserved gamma subunit, represented in Saccharomyces by Sss1p, that forms part of the heterotrimeric Sec61 core. `DOI:10.1002/j.1460-2075.1993.tb06092.x` Esnault et al. 1993 showed that SSS1 is essential for yeast secretory-protein translocation and encodes a conserved ER membrane protein. `DOI:10.1074/jbc.M701840200` Feng et al. 2007 assayed Sss1p coimmunoprecipitation with Sbh1p and Sec61p in Saccharomyces cells.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding yeast carries a Sec61 translocon in the endoplasmic-reticulum membrane for co- and post-translational protein translocation. [DOI:10.1091/mbc.3.2.129]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding-yeast model in which Sbh1p and Sss1p were identified as conserved eukaryotic protein-translocation-complex components. [DOI:10.1038/367654a0]

Functions

Sec61-dependent ER protein translocation — The Sec61 translocon forms the ER membrane channel that moves substrate polypeptides across the membrane into the ER lumen or laterally into the ER membrane.
- GO:0005784 GO:0005784 identifies the Sec61 translocon complex as mediating cotranslational and posttranslational protein translocation events.
- DOI:10.1016/0092-8674(95)90077-2 Panzner et al. 1995 reconstituted yeast posttranslational protein transport with purified Sec proteins and Kar2p.

Mechanism graphs

Sec61 forms the ER protein channel (FUNCTION)

The Sec61 alpha subunit forms the ER protein-conducting channel, the Sec61 beta and gamma subunits associate with that channel in the Sec61 heterotrimer, and the complex resides in the ER membrane during substrate translocation.

Subject	Predicate	Object	Evidence
Sec61 alpha protein-conducting channel subunit	forms pore of	Sec61 translocon complex	`GO:0005784` GO:0005784 identifies the Sec61 alpha subunit as the protein-conducting channel core. `DOI:10.1091/mbc.3.2.129` Stirling et al. 1992 localized Saccharomyces Sec61p as an integral ER membrane protein.
Sec61 beta subunit	associates with	Sec61 alpha protein-conducting channel subunit	`DOI:10.1074/jbc.M701840200` Feng et al. 2007 showed that the Sbh1p transmembrane domain coimmunoprecipitates with Sec61p and Sss1p.
Sec61 gamma subunit	associates with	Sec61 alpha protein-conducting channel subunit	`DOI:10.1002/j.1460-2075.1993.tb06092.x` Esnault et al. 1993 identified Sss1p as a conserved ER membrane protein required for secretory-protein translocation.
Sec61 translocon complex	is embedded in	endoplasmic reticulum membrane	`GO:0005784` GO:0005784 defines Sec61 as an endoplasmic-reticulum membrane translocon complex.
Sec61 translocon complex	supports	Sec61-dependent ER protein translocation	`DOI:10.1016/0092-8674(95)90077-2` Panzner et al. 1995 reconstituted yeast posttranslational protein transport with purified Sec proteins and Kar2p.

Discussions

INTERPRETATION (RESOLVED): Should Sec62, Sec63, Kar2, or ribosomes be included as Sec61 translocon complex components? GO:0005784 exactly denotes the heterotrimeric Sec61 channel. Sec62, Sec63, and Kar2 participate in posttranslational transport with Sec61, and ribosomes engage Sec61 during cotranslational transport, but those factors are associated machinery rather than constituents of the Sec61 core.
INTERPRETATION (RESOLVED): Should the Sec61 beta subunit's Rtn1p-containing pool make Rtn1p a Sec61 translocon component? Sbh1p can interact with Rtn1p in complexes that do not contain Sec61p or Sss1p, so that ER-shaping pool is outside the Sec61 translocon boundary.

Evidence

GO:0005784 Gene Ontology cellular-component term for the Sec61 translocon complex.
GO:0032991 Gene Ontology cellular-component parent term for protein-containing complex.
GO:0005789 Gene Ontology cellular-component term for the endoplasmic reticulum membrane.
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:10.1038/367654a0 Hartmann et al. 1994, Evolutionary conservation of components of the protein translocation complex, Nature.
DOI:10.1002/j.1460-2075.1993.tb06092.x Esnault et al. 1993, The yeast SSS1 gene is essential for secretory protein translocation, and encodes a highly conserved protein of the endoplasmic reticulum, The EMBO Journal.
DOI:10.1016/0092-8674(95)90077-2 Panzner et al. 1995, Posttranslational protein transport in yeast reconstituted with a purified complex of Sec proteins and Kar2p, Cell.
DOI:10.1074/jbc.M701840200 Feng et al. 2007, The Transmembrane Domain Is Sufficient for Sbh1p Function, Its Association with the Sec61 Complex, and Interaction with Rtn1p, Journal of Biological Chemistry.

Curation history

2026-09-15T20:43:17Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-15T20:44:32Z codex · EXPANDED_RECORD — Added ER-membrane parthood, protein-complex parentage, exact Sec61 synonymy, Sec61p/Sbh1p/Sss1p components, Saccharomyces scope, GO/DOI evidence, a Sec61 protein-channel graph, and resolved core boundary interpretations.
2026-09-15T20:53:48Z codex · FIX_VALIDATION — Retargeted the Sec61 core-boundary discussion from the bare components section to concrete Sec61p, Sbh1p, and Sss1p component anchors.
2026-09-15T21:06:29Z codex · ADDRESS_REVIEW — Resolved #1025 by narrowing the Saccharomyces canonical example to the Hartmann et al. component-conservation evidence and resolved #1026 by changing Sec61 beta/gamma labels and notes from yeast gene-product wording to source-neutral component classes.

Source: data/structures/other/sec61_translocon_complex.yaml