SAR1A

SAR1 is a G - protein that is involved in the transport between the endoplasmic reticulum (ER ) and the Golgi apparatus. It is found in eukaryotes. In plants and mammals there are two isoforms.

By GTP / PREB activated Sar1a the signal conveyed to the formation of the envelope ( COPII ) that vesicles which effect the transport of proteins from the ER to the Golgi. Initiated the formation of COPII - shell is the fact that Sar1a is loaded in the interaction with the ER membrane protein SEC12 with GTP. After binding of GTP a conformational change takes place at the N-terminal amphipathic helix is ​​disclosed. This amphipathic helix permits the attachment of Sar1a to the ER membrane. As a result, the other COPII coat proteins can attach to Sar1a.

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

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