One of two multimeric complexes that forms a membrane vesicle coat. The mammalian COPI subunits are called alpha-, beta-, beta'-, gamma-, delta-, epsilon- and zeta-COP. Vesicles with COPI coats are found associated with Golgi membranes at steady state. [ GOC:mah http://www.ncbi.nlm.nih.gov/pubmed/11252894 ]
Synonyms: coatomer