Explain what the COPII system does and how it works.
COPII: vesicular transport from ER to Golgi.
Sec12 (GEF) activates Sec1 (Ras-GTPase)
Sar1-GTP is integrated into the membrane and recruits Sec23/24
“bulge” in the membrane, “inner cage”
Sec13/31 are recruited
“outer cage”
vesicle is sealed and released
This process requires a LOT of energy.
How are vesicles fused to the Golgi?
Golgi uses tethers to “catch” the vesicle (ping-pong)
coiled coil tethers, 200 nm
multi-subunit tetherin complexes, 30 nm
For the fusion with the membrane, SNAREs are needed
vesicle: synaptobrevin
Golgi: syntaxin, SNAP-25
SNARE-zipping
recycling after fusion
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