COPII

COPII is a type of vesicle coat protein that transports proteins from the rough endoplasmic reticulum to the Golgi apparatus. This process is termed anterograde transport, in contrast to the retrograde transport associated with the COPI protein. The name "COPII" refers to the specific coat protein complex that initiates the budding process. The coat consists of large protein subcomplexes that are made of four different protein subunits.

Coat proteins

There are two protein heterodimers that form the coat complex. These proteins are

These proteins alone are not able to cause the budding of the vesicle or direct the vesicle to the correct target membrane. SNARE, cargo, and other proteins are also needed for these processes to occur. The CopII protein does, however, cause the binding that forms vesicle coat, and thereby causes the release from the ER. The exact process of how the vesicle is brought to a particular location, or how that location is determined is not yet known.