COPII

COPII‏‎ is a type of coat protein that is involved in the transport of proteins from the endoplasmic reticulum (ER) to the Golgi apparatus. This process is known as ER to Golgi transport, which is a crucial step in the secretory pathway of eukaryotic cells.

Structure

COPII is composed of five different proteins: Sec23, Sec24, Sec13, Sec31, and Sar1. These proteins assemble into a coat that surrounds transport vesicles as they bud from the ER. The assembly of the COPII coat is regulated by the GTPase activity of Sar1.

Function

The primary function of COPII is to transport proteins from the ER to the Golgi apparatus. This is achieved by the formation of transport vesicles that bud from the ER, which are then transported to the Golgi apparatus where they fuse and deliver their cargo. The proteins transported by COPII include both soluble proteins that reside in the lumen of the ER and transmembrane proteins that are embedded in the ER membrane.

Role in Disease

Mutations in the genes encoding COPII proteins have been linked to several human diseases, including Cranio-lenticulo-sutural dysplasia and Cole-Carpenter syndrome. These diseases are characterized by skeletal abnormalities, and are thought to result from defects in the transport of specific proteins that are important for bone development.

See Also

• Coat protein
• Endoplasmic reticulum
• Golgi apparatus
• ER to Golgi transport
• Secretory pathway
• Transport vesicle
• GTPase
• Soluble protein
• Transmembrane protein
• Cranio-lenticulo-sutural dysplasia
• Cole-Carpenter syndrome