Component of the coat protein complex II (COPII) which promotes the formation of transport vesicles from the endoplasmic reticulum (ER) (By similarity). The coat has two main functions, the physical deformation of the endoplasmic reticulum membrane into vesicles and the selection of cargo molecules (By similarity).
Subcellular locations: Cytoplasm, Cytoplasmic vesicle, COPII-coated vesicle membrane, Endoplasmic reticulum membrane
Associates with membranes in a GTP-dependent manner. Localizes to endoplasmic reticulum exit sites (ERES), also known as transitional endoplasmic reticulum (tER).