Identification and characterization of novel isoforms of COP I subunits

J Biochem. 2000 Nov;128(5):793-801. doi: 10.1093/oxfordjournals.jbchem.a022817.


COP I-coated vesicles are involved in vesicular trafficking in the early secretory pathway. The COP I coat is composed of seven subunits, alpha-, beta-, beta'-, gamma-, delta-, epsilon-, and zeta-COPs. Evidence suggests, however, that there may be isoforms of the COP I subunits. In the present study, we identified homologs of gamma-COP (gamma2-COP; original gamma-COP is referred to as gamma1-COP in this paper) and of zeta-COP (zeta2-COP; original zeta-COP is referred to as zeta1-COP). gamma1- and gamma2-COPs, and zeta1- and zeta2-COPs share 80 and 75%, respectively, of amino acids. mRNAs for gamma2-COP and zeta2-COP are expressed ubiquitously, suggesting their fundamental role in cellular function. Immunofluorescence analysis shows that gamma2-COP and zeta2-COP are colocalized with beta-COP in the paranuclear cis-Golgi region. Yeast two-hybrid analysis indicates that gamma1- and gamma2-COPs can directly, albeit promiscuously, interact with zeta1- and zeta2-COPs. Like gamma1-COP, gamma2-COP can form a complex with beta-COP in vivo. The gamma1-COP-containing and gamma2-COP-containing complexes can similarly interact with the cytoplasmic domain of p23. These results indicate that gamma2-COP and zeta2-COP can form a COP I-like complex in place of gamma1-COP and zeta1-COP, respectively, and suggest that the COP I complex and the COP I-like complex are functionally redundant.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Biological Transport, Active
  • Blotting, Northern
  • Blotting, Western
  • Cell Line
  • Coat Protein Complex I / chemistry*
  • Coat Protein Complex I / isolation & purification*
  • Molecular Sequence Data
  • Plasmids
  • Protein Conformation
  • RNA, Messenger / metabolism
  • Sequence Homology, Amino Acid


  • Coat Protein Complex I
  • RNA, Messenger

Associated data

  • GENBANK/AB047846
  • GENBANK/AB047847
  • GENBANK/AB047848
  • GENBANK/AB047849
  • GENBANK/AB047850