Tags: Protein.
COPI is a protein complex that coats vesicles transporting proteins from the cis end of the Golgi complex back to the rough endoplasmic reticulum (ER) where they were originally synthesized and between golgi compartments. This type of transport is termed as retrograde transport in contrast to the anterograde transport associated with the COPII protein. The name COPI refers to the specific coat protein complex that initiates the budding process on the cis-Golgi membrane.