Vesicular Trafficking I Flashcards
In regards to vesicular transport, vesicles __ off from primary compartment and ___ with the next one.
bud; fuse
contents of vesicle is called what
cargo
Is vesicular transport directional?
yes
vesicular transport mediates a ___ exchange of components between various membrane enclosed compartments
continous
composition of the membrane and ___ ___ on membrane surface provide cues for incoming traffic
molecular markers
combination of markers gives each compartment what?
its full address
retrieval pathways do what?
return molecules to source
Cells segregate proteins into membrane domains by assembling a special __ on cytosolic side of the membrane
coat
When transport vesicles bud off, are they coated or not?
coated
What are the 2 functions of the coat on vesicles?
concentrates select proteins in a specialized patch for transport; coat molds the vesicle to form a basket like lattice that deforms the membrane and gives shape to the vesicle
When is the vesicular coat discarded?
before vesicle fuses with target membrane
COPI and COPII are coats that mediate transport between what two cellular locations?
ER and Golgi
Clathrin-coated vesicles mediate transport from what two cellular location?
Golgi and plasma membrane
Which coated vesicle returns to ER from Golgi?
COPI
Which coated vesicle travels from ER to Golgi?
COPII
Describe the structure of clathrin
3 large and 3 small polypeptide chains form a triskelion
Triskelions assemble into what?
basket-like structures that form coated pits on cytosolic side of membrane
Adaptor proteins form a second layer between what?
cage and membrane
Assembly of the clathrin coat protein molecules introduces a ___ in the membrane; and leads to the formation of ___ __
curvature; coated buds
In regards to assembly of the clathrin coat, daptor proteins bind what?
clathrin and membrane-bound cargo receptors
These play a major role in coat assembly, vesicle formation, and protein trafficking?
Phosphoinositides (PI)
True or False?
Interconversions between various PI is highly compartmentalized. It is organelle and domain specific.
true
Different proteins bind with high specificity to the ___ of particular PI
headgroups
In regards to removal of the clathrin coat, what protein assembles a ring around the clathrin bud?
dynamin
Dynamin contains two domains. what are they?
PIP2 binding domain: tethers protein to membrane; GTPase domain: regulates rate of vesicle pinching
In regards to removal of the clathrin coat, ___ brings the 2 cytosolic sides of the membrane together and allows them to fuse
pinching
Dynamin recruits other proteins that do what to the lipid bilayer?
distort it
In regards to removal of clathrin coat, Hsp 70 chaperone protein uses ATP to do what?
peel off coat
In regards to vesicle targeting, specificity is achieved by what ?
surface markers on vesicles and complementary receptors on target membrane
In regards to vesicle targeting, this protein directs vesicle to specific spots on target membrane
Rab
In regards to vesicle targeting, this protein mediates fusion of vesicle with membrane
SNARE
The v-SNARE and T-SNARE interaction allows them to wrap around each other and form a bundle. The resulting SNARE complex does what?
locks the vesicle and target membrane together
What is the sequence of events in docking and fusion of vesicle?
Rab-GTP tethers with Rab-effector bringing vesicle in closer to target membrane. As docking occurs, V-SNARE and T-SNARE complex forms allowing the vesicle to fuse with the target membrane. Rab-GDP with bound GDI dissociates
After the vesicle has fused, what allows the SNARE complex to dissociate?
NSF and accessory protein separation by formation of ADP + Pi
In regards to transport from ER, what is quality control?
incompletely folded/misfolded proteins are retained in ER by binding to chaperone proteins such as BiP or calnexin and are then degraded
