alpha COP I: Proteins and Enzymes

Coatomer proteins are involved in regulating transport between the endoplasmic reticulum (ER) and the Golgi complex and in intra-Golgi transport. There exist two coatomer-protein mechanisms (COP I and COP II) and although they have mechanistic parallels, they are molecularly distinct. The COP I coat is comprised of seven subunits (alpha-, beta-, beta'-, gamma-, delta-, epsilon-, and zeta-COP) in a complex called coatomer. Assembly of the coatomer (COP I) onto non-clathrin coated vesicles is regulated by ADP-ribosylation factor (ARF). Vesicle formation, budding, fusion, and disassembly is dependent on GDP-GTP exchange, COP I, and ARF. COP I has been shown to facilitate retrograde intracellular transport from the ER to the Golgi complex. By contrast, COPII facilitates anterograde transport between these subcellular organelles. COP II has been shown to be independently and selectively recruited to the ER relative to COP I subunits.