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Mass / length primary structure 198 amino acids
Gene name (s) SAR1A , SAR1B

Sar1 is a G-protein involved in transport between the endoplasmic reticulum (ER) and the Golgi apparatus . It occurs in eukaryotes . There are two isoforms in plants and mammals .

Sar1a activated by GTP / PREB mediates the signal for the formation of the envelope (COPII) of those vesicles that bring about the transport of proteins from the ER to the Golgi. The formation of the COPII envelope is initiated by the fact that Sar1a is loaded with GTP in interaction with the ER membrane protein Sec12. After the binding of GTP there is a conformational change in which an N-terminal amphipathic helix is ​​exposed. This amphipathic helix enables Sar1a to attach to the ER membrane. As a result, the other COPII envelope proteins can attach to Sar1a.

Sar1b itself forms part of this shell, plays a role in the selection of the proteins to be transported, and is the trigger point for recycling the COPII shell. Mutations in SAR1B - gene can for chylomicron retention disease lead.

Individual evidence

  1. Kuge O, Dascher C, Orci L, et al : Sar1 promotes vesicle budding from the endoplasmic reticulum but not Golgi compartments . In: J. Cell Biol. . 125, No. 1, April 1994, pp. 51-65. PMID 8138575 . PMC 2120015 (free full text).
  2. Giulia Zanetti et al. : COPII and the regulation of protein sorting in mammals . In: Nature Cell Biology . 14, 2012, pp. 20-28. doi : 10.1038 / ncb2390 .
  3. UniProt Q9NR31 , UniProt Q9Y6B6
  4. Sato K: COPII coat assembly and selective export from the endoplasmic reticulum . In: J. Biochem. . 136, No. 6, December 2004, pp. 755-60. doi : 10.1093 / jb / mvh184 . PMID 15671485 .