Coat protein may refer to: Viral coat protein, a component of the capsid Variable surface glycoproteins or procyclins, surface coat proteins of either the bloodstream form or the procyclic form of the parasite Trypanosoma brucei COPI, a type of vesicle coat protein that transports proteins from the cis end of the Golgi complex back to the rough endoplasmic reticulum COPII, a type of vesicle coat protein that transports proteins from the rough endoplasmic reticulum to the Golgi apparatus