SAR1A
Description
The SAR1A (secretion associated Ras related GTPase 1A) is a protein-coding gene located on chromosome 10.
The Coat Protein Complex II, or COPII, is a group of proteins that facilitate the formation of vesicles to transport proteins from the endoplasmic reticulum to the Golgi apparatus or endoplasmic-reticulum–Golgi intermediate compartment. This process is termed anterograde transport, in contrast to the retrograde transport associated with the COPI complex. COPII is assembled in two parts: first an inner layer of Sar1, Sec23, and Sec24 forms; then the inner coat is surrounded by an outer lattice of Sec13 and Sec31.
== Function == The COPII coat is responsible for the formation of vesicles from the endoplasmic reticulum (ER). These vesicles transport cargo proteins to the Golgi apparatus (in yeast) or the endoplasmic-reticulum-Golgi intermediate compartment (ERGIC, in mammals). Coat assembly is initiated when the cytosolic Ras GTPase Sar1 is activated by its guanine nucleotide exchange factor Sec12. Activated Sar1-GTP inserts itself into the ER membrane, binding preferentially to areas of membrane curvature. As Sar1-GTP inserts into the membrane, it recruits Sec23 and Sec24 to make up the inner cage. Once the inner coat is assembled, the outer coat proteins Sec13 and Sec31 are recruited to the budding vesicle. Hydrolysis of the Sar1 GTP to GDP promotes disassembly of the coat.
SAR1A is involved in protein transport from the endoplasmic reticulum (ER) to the Golgi apparatus. It is required to maintain the localization of SEC16A at specific sites on the ER membrane, possibly by preventing its dissociation. The assembly of SEC16A on the ER membrane, which is dependent on SAR1A-GTP, forms a scaffold that defines ER exit sites (ERES).
SAR1A is also known as SAR1, SARA1, Sara, masra2.
Associated Diseases
- chylomicron retention disease
- sickle cell anemia
- nonpapillary renal cell carcinoma
- hyperinsulinemic hypoglycemia, familial, 4
- cancer
- glioblastoma
