The transport of proteins from the endoplasmic reticulum to the Golgi requires the assembly of a Coat Protein II (COPII) complex at certain sites on the membrane. These are known as endoplasmic reticulum exit sites (ERES) or transitional ER sites. The SEC16A gene encodes a peripheral membrane protein that is responsible for COPII vesicles coating, defining the transitional ER sites, endoplasmic reticulum organization and regulating secretory cargo traffic from the endoplasmic reticulum to the Golgi apparatus. The protein is recruited to the ER membrane by SAR1 and it has been found to interact with the COPII components SEC23A and SEC13.