Component of the coat protein complex II (COPII) which promotes the formation of transport vesicles from the endoplasmic reticulum (ER). The coat has two main functions, the physical deformation of the endoplasmic reticulum membrane into vesicles and the selection of cargo molecules (By similarity). Component of the COPII coat. Expressed in late sporogonial stages. Belongs to the SEC23/SEC24 family. SEC23 subfamily.