SEC31B (SEC31 Homolog B, COPII Coat Complex Component): SEC31B is a protein that is a key part of the COPII complex, which facilitates the transport of proteins from the endoplasmic reticulum (ER) to the Golgi apparatus. It is essential for proper protein secretion and the maintenance of organelle integrity. Mutations in SEC31B can impair protein transport and contribute to ER stress-related disorders.