COPI-coated vesicles function in retrograde transport from the Golgi to the ER, and in intra-Golgi transport. This is the platform subdomain of the coatomer gamma subunit appendage domain. It carries a protein-protein interaction site at UniProt:P53620, residue W776, which in yeast binds to the ARFGAP Glo3p, and in mammalian gamma-COP binds to a Glo3p orthologue, ARFGAP2 [1].

1: Gamma-COP appendage domain - structure and function. Watson PJ, Frigerio G, Collins BM, Duden R, Owen DJ; Traffic. 2004;5:79-88. PMID:14690497