Identification and characterization of novel isoforms of COP I subunits.

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.
Mesh Terms:
Amino Acid Sequence, Biological Transport, Active, Blotting, Northern, Blotting, Western, Cell Line, Coat Protein Complex I, Molecular Sequence Data, Plasmids, Protein Conformation, RNA, Messenger, Sequence Homology, Amino Acid
J. Biochem.
Date: Nov. 01, 2000
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