Sec16 is a determinant of transitional ER organization

Curr Biol. 2005 Aug 23;15(16):1439-47. doi: 10.1016/j.cub.2005.06.065.


Background: Proteins are exported from the ER at transitional ER (tER) sites, which produce COPII vesicles. However, little is known about how COPII components are concentrated at tER sites. The budding yeast Pichia pastoris contains discrete tER sites and is, therefore, an ideal system for studying tER organization.

Results: We show that the integrity of tER sites in P. pastoris requires the peripheral membrane protein Sec16. P. pastoris Sec16 is an order of magnitude less abundant than a COPII-coat protein at tER sites and seems to show a saturable association with these sites. A temperature-sensitive mutation in Sec16 causes tER fragmentation at elevated temperature. This effect is specific because when COPII assembly is inhibited with a dominant-negative form of the Sar1 GTPase, tER sites remain intact. The tER fragmentation in the sec16 mutant is accompanied by disruption of Golgi stacks.

Conclusions: Our data suggest that Sec16 helps to organize patches of COPII-coat proteins into clusters that represent tER sites. The Golgi disruption that occurs in the sec16 mutant provides evidence that Golgi structure in budding yeasts depends on tER organization.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • COP-Coated Vesicles / metabolism*
  • Computational Biology
  • Endoplasmic Reticulum / metabolism*
  • Endoplasmic Reticulum / physiology
  • Golgi Apparatus / metabolism*
  • Golgi Apparatus / ultrastructure
  • Immunoblotting
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Microscopy, Electron
  • Microscopy, Fluorescence
  • Molecular Sequence Data
  • Mutation / genetics
  • Nuclear Pore Complex Proteins
  • Pichia
  • Protein Transport / physiology
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Sequence Alignment
  • Sequence Analysis, DNA
  • Temperature


  • Membrane Proteins
  • Nuclear Pore Complex Proteins
  • SEC13 protein, S cerevisiae
  • SEC16 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins

Associated data

  • GENBANK/DQ115396