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Gene Review

SEC61  -  translocon subunit SEC61

Saccharomyces cerevisiae S288c

Synonyms: L3502.5, Protein transport protein SEC61, Sec61 complex subunit SEC61, Sec61 complex subunit alpha, YLR378C
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Disease relevance of SEC61

  • Moreover, Sec61-gamma and SSS1p are structurally related to SecEp of E. coli and to putative homologues in various other bacteria [1].

High impact information on SEC61

  • In vitro assembled yeast ribosome-nascent chain complexes (RNCs) containing a signal sequence in the nascent chain were immunopurified and reconstituted with the purified protein-conducting channel (PCC) of yeast endoplasmic reticulum, the Sec61 complex [2].
  • Together with the TRAM protein, Sec61p provides a site in the membrane, at the interface of channel and lipid, through which a TM domain can dynamically equilibrate between the lipid and aqueous phases, depending on the hydrophobicity of the TM domain and the length of the polypeptide segment tethering it to the ribosome [3].
  • While bound to Sec61p, the signal sequence forms a helix that is contacted on one side by Sec62p and Sec71p [4].
  • Cross-linking studies indicate that the signal sequence interacts in a Kar2p- and ATP-independent reaction with Sec61p, the multispanning membrane component of the protein-conducting channel, by intercalation into transmembrane domains 2 and 7 [4].
  • Oligomeric rings of the Sec61p complex induced by ligands required for protein translocation [5].

Biological context of SEC61


Anatomical context of SEC61


Associations of SEC61 with chemical compounds

  • Glycopeptide export was severely impaired, however, in several sec61 mutants that were only marginally defective in misfolded protein export [15].
  • Sec63p associates with several other proteins, including Sec61p, a 31.5-kDa glycoprotein, and a 23-kDa protein, and together with these proteins may constitute part of the polypeptide translocation apparatus [16].
  • cDNA cloning of a Sec61 homologue from the cryptomonad alga Pyrenomonas salina [17].

Physical interactions of SEC61


Regulatory relationships of SEC61


Other interactions of SEC61

  • Here we show that Sec61, Sec62 and Sec63 are assembled with two additional proteins into a multisubunit membrane-associated complex [21].
  • The first extragenic Sec sixty-one suppressor, SSS1, is an essential single copy gene whose overexpression restores translocation in the sec61 mutant [7].
  • Previously, we identified SEB1/SBH1, encoding the beta subunit of the Sec61p ER translocation complex, as a multicopy suppressor of the sec15-1 mutant, defective for one subunit of the exocyst complex [22].
  • The Candida albicans orthologue of the SPC3 gene, which encodes one of the subunits essential for the activity of the signal peptidase complex in Saccharomyces cerevisiae, was isolated by complementation of a thermosensitive mutation in the S. cerevisiae SEC61 gene [23].
  • Complete import of CPY into the lumen of the ER requests a new targeting mechanism for retrograde transport of the malfolded enzyme through the Sec61 channel to occur [24].

Analytical, diagnostic and therapeutic context of SEC61

  • We show by electron microscopy that purified mammalian and yeast Sec61p complexes in detergent form cylindrical oligomers with a diameter of approximately 85 A and a central pore of approximately 20 A. Each oligomer contains 3-4 heterotrimers [5].
  • Based on a co-immunoprecipitation of major histocompatibility complex (MHC) class I heavy-chain breakdown intermediates with the translocon subunit Sec61p, it was speculated that Sec61p maybe involved in retrograde transport [25].
  • Cryo-electron microscopy of the ribosome-Sec61 complex and a three-dimensional reconstruction showed that the Sec61 oligomer is attached to the large ribosomal subunit by a single connection [26].


  1. Evolutionary conservation of components of the protein translocation complex. Hartmann, E., Sommer, T., Prehn, S., Görlich, D., Jentsch, S., Rapoport, T.A. Nature (1994) [Pubmed]
  2. Architecture of the protein-conducting channel associated with the translating 80S ribosome. Beckmann, R., Spahn, C.M., Eswar, N., Helmers, J., Penczek, P.A., Sali, A., Frank, J., Blobel, G. Cell (2001) [Pubmed]
  3. The Sec61p complex mediates the integration of a membrane protein by allowing lipid partitioning of the transmembrane domain. Heinrich, S.U., Mothes, W., Brunner, J., Rapoport, T.A. Cell (2000) [Pubmed]
  4. Signal sequence recognition in posttranslational protein transport across the yeast ER membrane. Plath, K., Mothes, W., Wilkinson, B.M., Stirling, C.J., Rapoport, T.A. Cell (1998) [Pubmed]
  5. Oligomeric rings of the Sec61p complex induced by ligands required for protein translocation. Hanein, D., Matlack, K.E., Jungnickel, B., Plath, K., Kalies, K.U., Miller, K.R., Rapoport, T.A., Akey, C.W. Cell (1996) [Pubmed]
  6. A protein translocation defect linked to ubiquitin conjugation at the endoplasmic reticulum. Sommer, T., Jentsch, S. Nature (1993) [Pubmed]
  7. The yeast SSS1 gene is essential for secretory protein translocation and encodes a conserved protein of the endoplasmic reticulum. Esnault, Y., Blondel, M.O., Deshaies, R.J., Scheckman, R., Képès, F. EMBO J. (1993) [Pubmed]
  8. Multiple genes are required for proper insertion of secretory proteins into the endoplasmic reticulum in yeast. Rothblatt, J.A., Deshaies, R.J., Sanders, S.L., Daum, G., Schekman, R. J. Cell Biol. (1989) [Pubmed]
  9. Inactivation of the endoplasmic reticulum protein translocation factor, Sec61p, or its homolog, Ssh1p, does not affect peroxisome biogenesis. South, S.T., Baumgart, E., Gould, S.J. Proc. Natl. Acad. Sci. U.S.A. (2001) [Pubmed]
  10. The sequence of a 15 769 bp segment of Pichia anomala identifies the SEC61 and FBP1 genes and five new open reading frames. Ruíz, T., Sánchez, M., De la Rosa, J.M., Rodríguez, L., Domínguez, A. Yeast (2001) [Pubmed]
  11. A second trimeric complex containing homologs of the Sec61p complex functions in protein transport across the ER membrane of S. cerevisiae. Finke, K., Plath, K., Panzner, S., Prehn, S., Rapoport, T.A., Hartmann, E., Sommer, T. EMBO J. (1996) [Pubmed]
  12. Homologs of the yeast Sec complex subunits Sec62p and Sec63p are abundant proteins in dog pancreas microsomes. Tyedmers, J., Lerner, M., Bies, C., Dudek, J., Skowronek, M.H., Haas, I.G., Heim, N., Nastainczyk, W., Volkmer, J., Zimmermann, R. Proc. Natl. Acad. Sci. U.S.A. (2000) [Pubmed]
  13. Membrane topology and function of Der3/Hrd1p as a ubiquitin-protein ligase (E3) involved in endoplasmic reticulum degradation. Deak, P.M., Wolf, D.H. J. Biol. Chem. (2001) [Pubmed]
  14. Sec61p-independent degradation of the tail-anchored ER membrane protein Ubc6p. Walter, J., Urban, J., Volkwein, C., Sommer, T. EMBO J. (2001) [Pubmed]
  15. The protein translocation channel mediates glycopeptide export across the endoplasmic reticulum membrane. Gillece, P., Pilon, M., Römisch, K. Proc. Natl. Acad. Sci. U.S.A. (2000) [Pubmed]
  16. Topology and functional domains of Sec63p, an endoplasmic reticulum membrane protein required for secretory protein translocation. Feldheim, D., Rothblatt, J., Schekman, R. Mol. Cell. Biol. (1992) [Pubmed]
  17. cDNA cloning of a Sec61 homologue from the cryptomonad alga Pyrenomonas salina. Müller, S.B., Rensing, S.A., Martin, W.F., Maier, U.G. Curr. Genet. (1994) [Pubmed]
  18. SSS1 encodes a stabilizing component of the Sec61 subcomplex of the yeast protein translocation apparatus. Esnault, Y., Feldheim, D., Blondel, M.O., Schekman, R., Képès, F. J. Biol. Chem. (1994) [Pubmed]
  19. Subunits of the translocon interact with components of the oligosaccharyl transferase complex. Chavan, M., Yan, A., Lennarz, W.J. J. Biol. Chem. (2005) [Pubmed]
  20. Membrane insertion of uracil permease, a polytopic yeast plasma membrane protein. Silve, S., Volland, C., Garnier, C., Jund, R., Chevallier, M.R., Haguenauer-Tsapis, R. Mol. Cell. Biol. (1991) [Pubmed]
  21. Assembly of yeast Sec proteins involved in translocation into the endoplasmic reticulum into a membrane-bound multisubunit complex. Deshaies, R.J., Sanders, S.L., Feldheim, D.A., Schekman, R. Nature (1991) [Pubmed]
  22. The beta subunit of the Sec61p endoplasmic reticulum translocon interacts with the exocyst complex in Saccharomyces cerevisiae. Toikkanen, J.H., Miller, K.J., Söderlund, H., Jäntti, J., Keränen, S. J. Biol. Chem. (2003) [Pubmed]
  23. Characterization of Candida albicans orthologue of the Saccharomyces cerevisiae signal-peptidase-subunit encoding gene SPC3. De La Rosa, J.M., González, J.M., Gutiérrez, F., Ruíz, T., Rodríguez, L. Yeast (2004) [Pubmed]
  24. Endoplasmic reticulum degradation. Reverse protein transport and its end in the proteasome. Plemper, R.K., Wolf, D.H. Mol. Biol. Rep. (1999) [Pubmed]
  25. Mutant analysis links the translocon and BiP to retrograde protein transport for ER degradation. Plemper, R.K., Böhmler, S., Bordallo, J., Sommer, T., Wolf, D.H. Nature (1997) [Pubmed]
  26. Alignment of conduits for the nascent polypeptide chain in the ribosome-Sec61 complex. Beckmann, R., Bubeck, D., Grassucci, R., Penczek, P., Verschoor, A., Blobel, G., Frank, J. Science (1997) [Pubmed]
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