Receptor-induced polymerization of coatomer

Coatomer, the coat protein complex of COPI vesicles, is involved in the bud ding of these vesicles, but the underlying mechanism is unknown. Toward a b etter understanding of this process, the interaction between coatomer and t he cytoplasmic domain of a major transmembrane protein of COPI vesicles, p2 3, was studied. Interaction of coatomer with this peptide domain results in a conformational change and polymerization of the complex in vitro. This c hanged conformation also is observed in vivo, i.e., on the surface of authe ntic, isolated COPI vesicles. An average of four peptides was found associa ted with one coatomer complex after polymerization. Based on these results, we propose a mechanism by which the induced conformational change of coato mer results in its polymerization, and thus drives formation of the bud on the Golgi membrane during biogenesis of a COPI vesicle.