Lec11 - speed review

Oligosaccharyl Transferase

ER luminal enzyme that transfers the 14-sugar precursor from dolichol onto an Asparagine (Asn-X-Ser/Thr) side chain during N-linked glycosylation.

Glucosyl Transferase

ER quality-control sensor that recognizes misfolded proteins and re-attaches a single glucose, sending them back to Calnexin/Calreticulin for another folding attempt.

Glucosidases I & II

ER luminal enzymes that trim terminal glucoses off the N-linked oligosaccharide as a protein folds.

Calnexin & Calreticulin

ER luminal chaperones that bind monoglucosylated glycoproteins to assist folding and prevent misfolded protein export.

Sar1-GEF & Sar1 Activation

Transmembrane ER protein (Sar1-GEF) exchanges GDP for GTP on Sar1. Sar1-GTP exposes an amphipathic $\alpha$-helix, anchoring into the ER membrane to recruit the COPII coat.

COPII Coat Composition

Sar1 GTPase + Sec23/Sec24 (inner coat) + Sec13/Sec31 (outer coat). Transports anterograde (ER $\rightarrow$ Golgi). Sec23 acts as a GAP for Sar1 uncoating.

COPI Coat Composition

ARF GTPase + inner coat ($\beta, \gamma, \delta, \zeta$) + outer coat ($\alpha, \beta', \epsilon$). Transports retrograde (Golgi $\rightarrow$ ER).

Dynamin

GTPase that forms a helical collar around the neck of budding Clathrin-coated vesicles and uses GTP hydrolysis to physically pinch off the vesicle.

v-SNARE & t-SNAREs

v-SNARE (vesicle) and t-SNAREs (target) twist into a 4-helix trans-SNARE complex, squeezing out water to catalyze membrane fusion.

NSF ATPase

Ring-shaped ATPase that uses ATP hydrolysis to disassemble the intertwined cis-SNARE complex post-fusion so SNAREs can be recycled.

Rab-GTP & Rab Effector

Active Rab-GTP on the vesicle binds a Rab effector (tethering protein) on the target membrane to drive vesicle tethering/docking.