Lecture 5 Flashcards
What is different about the membrane of different compartments of the endomembrane system?
Their lipid compositions
What is the function of SAR1-GEF?
SAR1-GEF activates SAR1-GTP which exposes an amphipathic helix which inserts itself onto the ER membrane.
What are Sec23 and Sec24?
The inner coat subunits of COP2.
Which proteins does bind Sec23 on the ER membrane?
SAR1-GTP which is found bound to the ER membrane.
Sec24 binds Sec23 laterally.
What is the name of the outer layer COP2 proteins? What is their function?
Sec13 and Sec31 these proteins polymerize on the outer layer of the COP2 complex which folds the ER membrane to form a vesicle.
How is cargo that enters the vesicle chosen?
Cargo receptors on the ER membrane which bind cargo to the COP2 coat.
What is the function of Sar1-GEF?
Sar1-GEF is a GEF protein that activates Sar1-GTP which is essential for assembly of the COP2 coat.
What are SNARE molecules?
SNARE molecules are proteins inserted into vesicles and on target membranes and these proteins combine with each other to form the coils which allow fusion to occur between vesicle and target membrane.
What are Rab-GTPases?
Small GTPase proteins that are loaded onto vesicles. These proteins associate with SNARE proteins to permit fusion of the membrane.
What is the function of Rab-GTP?
Rab proteins bind Rab effectors which tether the vesicle to the location of the t-SNAREs allowing the v-SNAREs to interact with them.
How many SNAREs interact with each other in one time?
4; 3 t-SNAREs with 1 v-SNARE
How do SNAREs interact with each other?
hydrophobic regions locations promote supercoiling of the SNAREs in such a way that it forces the vesicle’s membrane to interact with the target membrane while also forcing the water molecules out of the way.
What kind of domain do SNARE proteins have which interact with each other during membrane fusion?
Special alpha helices where hydrophobic regions line one side of the seam. The hydrophobic regions coil around the individual SNARE protein.
What differentiate Q-SNAREs from R-SNAREs?
The amino acids at the zero position; Glutamine for Q and Arginine for R.
Example of Q-SNARE:
t-SNARE
