BMED 5207 Vesicles from ER exit sites to cis-golgi transport (exam 3)

Step 1: Vesicles from ER exit sites to cis-golgi transport

Sar1-GDP binds to its ER-specific GEF, which catalyzes the release of GDP from SAR1, allowing a GTP molecule to bind Sar1

Step 2: Vesicles from ER exit sites to cis-golgi transport

GTP binding alters the conformation of Sar1, its amphipathic N-terminal alpha helix becomes exposed. This N-terminus anchors Sar1-GTP to the cytosolic leaflet of ER membrane

Step 3: Vesicles from ER exit sites to cis-golgi transport

Sar1-GTP recruits the first layer of the COPII coat

Step 4: Vesicles from ER exit sites to cis-golgi transport

COPII coat recruits a v-SNARE

Step 5: Vesicles from ER exit sites to cis-golgi transport

COPII coat recruits transmemembrane cargo proteins and transmembrane cargo receptors

Step 6: Vesicles from ER exit sites to cis-golgi transport

the pre-budding complex recruits the second layer of the COPII coat. This second layer clusters the first-layer comolexes. This assembled coat pinches off the vesicle

Step 7: Vesicles from ER exit sites to cis-golgi transport

Sar1 hydrolyses GTP and this desatbilize sthe coat and Sar1 dissociates fro mthe vesicle

Step 8: Vesicles from ER exit sites to cis-golgi transport

the vesicle sheds its coat

step 9: Vesicles from ER exit sites to cis-golgi transport

the vesicle becomes tetherd to the ERGIC/ cis-Golgi by a tether and Rab1-GTP

step 10: Vesicles from ER exit sites to cis-golgi transport

interaction of v-SNARE and t-SNARE causes membrane fusion

step 11: Vesicles from ER exit sites to cis-golgi transport

a-SNAP-NSF unwinds the v/t-SNARE complex

step 12: Vesicles from ER exit sites to cis-golgi transport

large anterograde carriers move cargo along microtubules towards the Golgi; during thier movement towards the golgi, large anterograde carriers shed COPI vesicles to recycle proteins/membrane to the ERGIC. Large anterograde carriers fuse with each other and recieve COPI vesicles from the Golgi to form the cis-golgi