SEC31B (SEC31 Homolog B, COPII Coat Complex Component): SEC31B is a protein that forms a crucial part of the COPII complex, which enables the transport of proteins from the endoplasmic reticulum (ER) to the Golgi apparatus. It is vital for correct protein secretion and the preservation of organelle integrity. Mutations in SEC31B can disrupt protein transport and lead to ER stress-related conditions.