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Gene Review

SEC21  -  Sec21p

Saccharomyces cerevisiae S288c

Synonyms: Coatomer subunit gamma, Gamma-COP, Gamma-coat protein, N0543, YNL287W
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High impact information on SEC21

  • Comparison with other yeast mutants indicates that Sec21p (gamma-COP) and Sec20p (an endoplasmic reticulum membrane protein) are also involved primarily, if not exclusively, in retrograde transport [1].
  • Coatomer from beta'-COP (sec27-1) and alpha-COP (ret1-1) mutants, but not from gamma-COP (sec21) mutants, had lost the ability to bind dilysine motifs in vitro [2].
  • Here we describe the characterization of SEC21, an essential gene required for protein transport from the endoplasmic reticulum to the Golgi in the yeast Saccharomyces cerevisiae [3].
  • To investigate the direct and primary role(s) of COPI in ER/Golgi transport and in the secretory pathway in general, we used PCR-based mutagenesis to generate new temperature-conditional mutant alleles of one COPI gene in Saccharomyces cerevisiae, SEC21 (gamma-COP) [4].
  • Additionally, the sec21 mutants exhibited early Golgi-specific glycosylation defects and structural aberrations in early but not late Golgi compartments at nonpermissive temperature [4].

Biological context of SEC21

  • SEC21 is a gene required for ER to Golgi protein transport that encodes a subunit of a yeast coatomer [3].
  • On the basis of mutations in the yeast homologue of gamma-COP, Sec21p, a second binding site is proposed to exist on the gamma-COP appendage that interacts with the alpha,beta',epsilon COPI subcomplex [5].

Anatomical context of SEC21


Other interactions of SEC21

  • SEC21 encodes the gamma-subunit of coatomer, a heptameric protein complex that together with Arf1p forms the COPI coat [8].
  • A bfr1-delta 1::URA3 deletion strain is viable, but has defects in cell morphology and nuclear segregation, and the mutation accentuates the growth and secretion defects of a sec21 mutant [9].
  • Interestingly, the inviability of strains bearing several mutant alleles of DSL1 can be suppressed by expression of either Erv14p (a protein required for the movement of a specific protein from the ER to the Golgi), Sec21p (the gamma-subunit of the COPI coat protein complex coatomer), or Sly1-20p [10].


  1. SNARE-mediated retrograde traffic from the Golgi complex to the endoplasmic reticulum. Lewis, M.J., Pelham, H.R. Cell (1996) [Pubmed]
  2. Coatomer is essential for retrieval of dilysine-tagged proteins to the endoplasmic reticulum. Letourneur, F., Gaynor, E.C., Hennecke, S., Démollière, C., Duden, R., Emr, S.D., Riezman, H., Cosson, P. Cell (1994) [Pubmed]
  3. SEC21 is a gene required for ER to Golgi protein transport that encodes a subunit of a yeast coatomer. Hosobuchi, M., Kreis, T., Schekman, R. Nature (1992) [Pubmed]
  4. COPI-independent anterograde transport: cargo-selective ER to Golgi protein transport in yeast COPI mutants. Gaynor, E.C., Emr, S.D. J. Cell Biol. (1997) [Pubmed]
  5. Gamma-COP appendage domain - structure and function. Watson, P.J., Frigerio, G., Collins, B.M., Duden, R., Owen, D.J. Traffic (2004) [Pubmed]
  6. Ultrastructural modifications of vesicular and Golgi elements in the Saccharomyces cerevisiae sec21 mutant at permissive and non-permissive temperatures. Rambourg, A., Clermont, Y., Jackson, C.L., Képès, F. Anat. Rec. (1994) [Pubmed]
  7. Arabidopsis Sec21p and Sec23p homologs. Probable coat proteins of plant COP-coated vesicles. Movafeghi, A., Happel, N., Pimpl, P., Tai, G.H., Robinson, D.G. Plant Physiol. (1999) [Pubmed]
  8. The ADP ribosylation factor-nucleotide exchange factors Gea1p and Gea2p have overlapping, but not redundant functions in retrograde transport from the Golgi to the endoplasmic reticulum. Spang, A., Herrmann, J.M., Hamamoto, S., Schekman, R. Mol. Biol. Cell (2001) [Pubmed]
  9. BFR1, a multicopy suppressor of brefeldin A-induced lethality, is implicated in secretion and nuclear segregation in Saccharomyces cerevisiae. Jackson, C.L., Képès, F. Genetics (1994) [Pubmed]
  10. Dsl1p, an essential protein required for membrane traffic at the endoplasmic reticulum/Golgi interface in yeast. Vanrheenen, S.M., Reilly, B.A., Chamberlain, S.J., Waters, M.G. Traffic (2001) [Pubmed]
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