SSS1/YDR086C Summary Help

Standard Name SSS1 1
Systematic Name YDR086C
Feature Type ORF, Verified
Description Subunit of the Sec61p translocation complex (Sec61p-Sss1p-Sbh1p); this complex forms a channel for passage of secretory proteins through the endoplasmic reticulum membrane, and of the Ssh1p complex (Ssh1p-Sbh2p-Sss1p); interacts with Ost4p and Wbp1p (2, 3, 4, 5 and see Summary Paragraph)
Name Description Sec Sixty-one Suppressor 1
Chromosomal Location
ChrIV:617170 to 616928 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Gene Ontology Annotations All SSS1 GO evidence and references
  View Computational GO annotations for SSS1
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 6 genes
Classical genetics
reduction of function
Large-scale survey
51 total interaction(s) for 33 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 8
  • Affinity Capture-RNA: 6
  • Affinity Capture-Western: 10
  • Co-fractionation: 2
  • Co-purification: 2
  • PCA: 12
  • Two-hybrid: 2

Genetic Interactions
  • Dosage Rescue: 9

Expression Summary
Length (a.a.) 80
Molecular Weight (Da) 8,944
Isoelectric Point (pI) 10.26
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrIV:617170 to 616928 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..243 617170..616928 2011-02-03 1996-07-31
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000002493

Sss1p, a small essential protein, is a subunit of the heterotrimeric Sec61 complex, also referred to as the translocon (2, reviewed in 6). The Sec61 complex forms a channel in the endoplasmic reticulum (ER) membrane and mediates translocation of secretory and membrane proteins into the ER and also retrograde transport of misfolded proteins to the cytoplasm for degradation (reviewed in 7 and 8). The other subunits of the Sec61 complex include Sec61p, the major subunit that contains ten transmembrane domains and forms the protein-conducting channel, and Sbh1p (9, 10, reviewed in 6). Sss1p is also a subunit of the structurally related trimeric Ssh1p complex, consisting of Ssh1p, Sbh2p, and Sss1p, that is thought to function exclusively in cotranslational translocation (3).

Proteins that are transported into or across the ER membrane are directed there by signal sequences or by transmembrane segments that interact with the translocation apparatus. In S. cerevisiae the Sec61 complex mediates both co- and posttranslational translocation (while the mammalian Sec61 complex functions primarily with the cotranslational pathway; 11). During cotranslational translocation, ribosomes synthesizing signal sequence-containing proteins are targeted to the translocon via the signal recognition particle (SRP), and the ribosomes bind directly to Sec61p such that protein biosynthesis and translocation are synchronous (12). Posttranslational translocation requires Sec62p, Sec63p, Sec66p, and Sec72p (comprising the Sec63 complex), as well as Kar2p, in place of SRP to facilitate interaction of the full-length polypeptide with the translocon via the signal sequence (13, 14).

Retrograde transport of misfolded proteins into the cytoplasm (also called dislocation) employs the Sec61 channel via interaction with the 19S proteasome regulatory particle (15). This interaction, which competes with the ribosome-Sec61p interaction, defines the Sec61 complex as the principal proteasome receptor in the ER membrane (15).

SSS1 (for Sec Sixty-one Suppressor) overexpression restores translocation in the sec61-3 temperature sensitive mutant (1, 16). Sss1p interacts physically with Sec61p in a region including the transmembrane segments TM6, TM7, and TM8 (amino acids L232-R406), and functions to stabilize the translocation channel (2, 16). In addition, Sss1p exhibits physical interactions with some of the oligosaccharyltransferase (OST) subunits and thus may facilitate binding of OST to the channel to promote efficient N-linked glycosylation of glycoproteins (4, 5). Sss1p is an integral membrane protein and its amino terminal half is exposed to the cytosol (2).

Sss1p is conserved among organisms and the human homolog, Sec61 gamma, functionally complements an sss1 null mutation in S. cerevisiae (17). Bacterial and archaeal Sss1p orthologs are referred to as SecE (17, reviewed in 6).

Last updated: 2007-11-09 Contact SGD

References cited on this page View Complete Literature Guide for SSS1
1) Esnault Y, et al.  (1993) The yeast SSS1 gene is essential for secretory protein translocation and encodes a conserved protein of the endoplasmic reticulum. EMBO J 12(11):4083-93
2) Esnault Y, et al.  (1994) SSS1 encodes a stabilizing component of the Sec61 subcomplex of the yeast protein translocation apparatus. J Biol Chem 269(44):27478-85
3) Finke K, et al.  (1996) A second trimeric complex containing homologs of the Sec61p complex functions in protein transport across the ER membrane of S. cerevisiae. EMBO J 15(7):1482-94
4) Scheper W, et al.  (2003) Coordination of N-glycosylation and protein translocation across the endoplasmic reticulum membrane by Sss1 protein. J Biol Chem 278(39):37998-8003
5) Chavan MM, et al.  (2005) Subunits of the translocon interact with components of the oligosaccharyl transferase complex. J Biol Chem 280(24):22917-24
6) Osborne AR, et al.  (2005) Protein translocation by the Sec61/SecY channel. Annu Rev Cell Dev Biol 21():529-50
7) Sommer T and Wolf DH  (1997) Endoplasmic reticulum degradation: reverse protein flow of no return. FASEB J 11(14):1227-33
8) Romisch K  (1999) Surfing the Sec61 channel: bidirectional protein translocation across the ER membrane. J Cell Sci 112 ( Pt 23)():4185-91
9) Wilkinson BM, et al.  (1996) Determination of the transmembrane topology of yeast Sec61p, an essential component of the endoplasmic reticulum translocation complex. J Biol Chem 271(41):25590-7
10) Toikkanen J, et al.  (1996) Yeast protein translocation complex: isolation of two genes SEB1 and SEB2 encoding proteins homologous to the Sec61 beta subunit. Yeast 12(5):425-38
11) Ng DT, et al.  (1996) Signal sequences specify the targeting route to the endoplasmic reticulum membrane. J Cell Biol 134(2):269-78
12) Prinz A, et al.  (2000) Sec61p is the main ribosome receptor in the endoplasmic reticulum of Saccharomyces cerevisiae. Biol Chem 381(9-10):1025-9
13) Plath K, et al.  (1998) Signal sequence recognition in posttranslational protein transport across the yeast ER membrane. Cell 94(6):795-807
14) Panzner S, et al.  (1995) Posttranslational protein transport in yeast reconstituted with a purified complex of Sec proteins and Kar2p. Cell 81(4):561-70
15) Kalies KU, et al.  (2005) The protein translocation channel binds proteasomes to the endoplasmic reticulum membrane. EMBO J 24(13):2284-93
16) Wilkinson BM, et al.  (1997) Molecular architecture of the ER translocase probed by chemical crosslinking of Sss1p to complementary fragments of Sec61p. EMBO J 16(15):4549-59
17) Hartmann E, et al.  (1994) Evolutionary conservation of components of the protein translocation complex. Nature 367(6464):654-7