Ssh1 translocon complex

GO:0071261 · Other · Multiprotein complex · Proposed

An endoplasmic-reticulum translocon complex with a core heterotrimer of alpha, beta, and gamma subunits, represented in budding yeast by Ssh1p, Sbh2p, and Sss1p, that supports cotranslational protein transport across the ER membrane. [GO:0071261]

Synonyms: Ssh1p-Sss1p-Sbh2p complex; Ssh1p 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
Ssh1 alpha translocon subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	SSH1	UNKNOWN	Sec61-alpha paralog that supplies the large alpha core subunit of the Ssh1 ER translocon. `GO:0071261` GO:0071261 lists Ssh1p as one of the budding-yeast core proteins of the Ssh1 translocon complex. `PMID:8612571` Finke et al. 1996 identified Ssh1p in a second trimeric yeast ER translocon related to the Sec61p complex.
Sbh2 beta translocon subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	SBH2	UNKNOWN	Small beta subunit that joins Ssh1p and Sss1p in the heterotrimeric Ssh1 ER translocon core. `GO:0071261` GO:0071261 lists Sbh2p as one of the budding-yeast core proteins of the Ssh1 translocon complex. `PMID:8612571` Finke et al. 1996 identified Sbh2p in the Ssh1p-containing trimeric ER translocon.
Sss1 gamma translocon subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	SSS1	UNKNOWN	Small gamma subunit that joins Ssh1p and Sbh2p in the heterotrimeric Ssh1 ER translocon core. `GO:0071261` GO:0071261 lists Sss1p as one of the budding-yeast core proteins of the Ssh1 translocon complex. `PMID:8612571` Finke et al. 1996 identified Sss1p in the Ssh1p-containing trimeric ER translocon.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding yeast contains an ER-membrane Ssh1p complex composed of Ssh1p, Sbh2p, and Sss1p. [PMID:8612571]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Yeast model in which the Ssh1p/Sbh2p/Sss1p trimeric ER translocon was discovered and tied to protein transport. [PMID:8612571]

Functions

Ssh1-dependent cotranslational ER protein translocation — The Ssh1 translocon supports cotranslational translocation of a subset of signal-sequence-bearing substrates across the endoplasmic-reticulum membrane.
- GO:0071261 GO:0071261 defines Ssh1 as a translocon complex involved in the cotranslational pathway of protein transport across the ER membrane.
- PMID:8612571 Finke et al. 1996 discovered the Ssh1p complex in the Saccharomyces cerevisiae ER membrane and proposed that, unlike Sec61, it functions exclusively in cotranslational protein transport.
- DOI:10.1091/mbc.01-10-0518 Wittke et al. 2002 showed that Ssh1p physically approaches the SRP receptor beta subunit in vivo and recognizes a subset of ER signal sequences.

Mechanism graphs

Ssh1 supports cotranslational ER protein translocation (FUNCTION)

The Ssh1 translocon is an ER-membrane complex that functions in cotranslational protein translocation and recognizes a subset of signal-sequence-bearing substrates.

Subject	Predicate	Object	Evidence
Ssh1 alpha translocon subunit	is core subunit of	Ssh1 translocon complex	`GO:0071261` GO:0071261 names Ssh1p as a budding-yeast core protein of the Ssh1 translocon complex. `PMID:8612571` Finke et al. 1996 identified Ssh1p as a Sec61p-complex homolog in the second trimeric ER translocon.
Sbh2 beta translocon subunit	is core subunit of	Ssh1 translocon complex	`GO:0071261` GO:0071261 names Sbh2p as a budding-yeast core protein of the Ssh1 translocon complex. `PMID:8612571` Finke et al. 1996 identified Sbh2p as part of the Ssh1p-containing trimeric ER translocon.
Sss1 gamma translocon subunit	is core subunit of	Ssh1 translocon complex	`GO:0071261` GO:0071261 names Sss1p as a budding-yeast core protein of the Ssh1 translocon complex. `PMID:8612571` Finke et al. 1996 identified Sss1p as part of the Ssh1p-containing trimeric ER translocon.
Ssh1 translocon complex	is embedded in	endoplasmic reticulum membrane	`GO:0071261` GO:0071261 identifies Ssh1 as an ER translocon complex. `PMID:8612571` Finke et al. 1996 reported the Ssh1p/Sbh2p/Sss1p trimeric complex in the Saccharomyces cerevisiae ER membrane.
Ssh1 translocon complex	supports	Ssh1-dependent cotranslational ER protein translocation	`PMID:8612571` Finke et al. 1996 found that the Ssh1p complex interacts with membrane-bound ribosomes. `DOI:10.1091/mbc.01-10-0518` Wittke et al. 2002 confirmed proximity between Ssh1p and the SRP receptor beta subunit in vivo.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral groundings for the Ssh1 alpha subunit, Sbh2 beta subunit, and Sss1 gamma subunit. GO exactly grounds the Ssh1 translocon complex and Finke et al. established the budding-yeast Ssh1p/Sbh2p/Sss1p core, but exact source-neutral family CURIEs were not curated in this pass.
INTERPRETATION (RESOLVED): Should membrane-bound ribosomes or the SRP receptor beta subunit be included as Ssh1 translocon complex components? Membrane-bound ribosomes and the SRP receptor contact Ssh1 during cotranslational ER import, but the directly curated core is the Ssh1p/Sbh2p/Sss1p trimer.

Evidence

GO:0071261 Gene Ontology cellular-component term for the Ssh1 translocon complex.
GO:0071256 Gene Ontology cellular-component parent term for endoplasmic-reticulum translocon complexes.
GO:0005789 Gene Ontology cellular-component term for the endoplasmic reticulum membrane.
PMID:8612571 Finke et al. 1996, A second trimeric complex containing homologs of the Sec61p complex functions in protein transport across the ER membrane of S. cerevisiae, The EMBO Journal.
DOI:10.1091/mbc.01-10-0518 Wittke et al. 2002, Recognition of a subset of signal sequences by Ssh1p, a Sec61p-related protein in the membrane of endoplasmic reticulum of yeast Saccharomyces cerevisiae, Molecular Biology of the Cell.

Curation history

2026-09-18T21:42:03Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-18T21:43:23Z codex · EXPANDED_RECORD — Added Ssh1p-Sss1p-Sbh2p synonymy, translocon parentage, ER-membrane parthood, Saccharomyces scope, an Ssh1-dependent cotranslational translocation function, GO/PMID/DOI evidence, a nonmechanistic Ssh1 function graph, and a Ssh1 subunit-boundary TODO.
2026-09-18T22:09:00Z codex · ADDRESS_REVIEW — Resolved #1196 by adding Ssh1p/Sbh2p/Sss1p component rows and upgrading the graph to mechanistic scope, resolved #1197 by adding a ribosome and SRP receptor boundary discussion, and resolved #1198 by adding the Ssh1p complex exact synonym.
2026-09-18T22:09:31Z codex · NORMALIZE_ORDER — Moved Ssh1 component rows into the canonical components slot after part_of.

Source: data/structures/other/ssh1_translocon_complex.yaml