week 4 reading

Question 1

SAR1 function

Answer 1

specific SAR1 GEF binds to cytosolic SAR so it releases its GDP
GTP-bound state exposes amphiphilic a-helix (conformation change)

Question 2

coat disassembly

Answer 2

coat recruitment GTPases
GTP to GDP: hydrophobic tail pops out of membrane, coat disassembles

Question 3

Rab proteins: function

Answer 3

directs vesicles to spots on target membrane

Question 4

vesicular trafficking steps

Answer 4

cargo sorting
vesicle formation
vesicle trafficking
fusion
recycling

Question 5

cargo sorting: direct vs. indirect

Answer 5

transmembrane proteins: direct
soluble proteins: indirect (need sorting receptors)
- both have a tail that functions in sorting

Question 6

vesicle formation steps

Answer 6

coat assembly
bud formation
vesicle formation
pinching off
uncoating

Question 7

dynamin

Answer 7

large GTPase with multiple hydrolysis domains
cleaves neck of bud

Question 8

adaptor proteins

Answer 8

bind to cargo receptors to recruit coat proteins
also binds sorting signals, PIPs

Question 9

vesicle targeting: locations

Answer 9

cytoskeleton (actin, microtubules)
motors

Question 10

vesicle fusion: mediation

Answer 10

SNARE mediated

Question 11

SNARE protein fusion steps

Answer 11

1 v-SNARE attaches to 3 t-SNARES to create 4-helix bundle
pull vesicle closer so it can bind with membrane

Question 12

recycling: NSF

Answer 12

uses ATP to break SNARE complex

Question 13

recycling: SNAREs

Answer 13

trans to cis conformation

Question 14

Rab cascade

Answer 14

RabA recruits effector 1 and RabB-GEF
RabB becomes GTP-bound
RabB recruits effector 2, RabA-GAP
RabA-GTP hydrolyzed, RabA-GDP tucks tail into membrane and leaves

Question 15

post-golgi trafficking: 3 types

Answer 15

secretion
constituted secretion - PM
lysosomes

Question 16

regulated secretion

Answer 16

processing: typically proteolysis
signaling @ PM: vesicles trafficked to PM to release cargo

Question 17

lysosome structure/characteristics

Answer 17

acidic lumen due to v-ATPase
- contains acid hydrolases
transporters
- recycle AAs, other components

Question 18

lysosomal maturation

Answer 18

fuse with other organelles
- phagosomes, autophagosomes, late endosomes
- fuse, eventually become standard lysosome again

Question 19

lysosomal sorting

Answer 19

based on pH
ER>Golgi>Endosome
higher affinity in golgi

Question 20

M6P

Answer 20

from TGN, AP + clathrin mediates fusion with lysosome via SNAREs
M6P enters lysosome, stays in lysosome when M6PR loses affinity for it
M6PR returns to TGN

Question 21

4 types of endocytosis

Answer 21

non-clathrin mediated:
caveolae
macropinocytosis

clathrin-mediated:
pinocytosis
receptor-mediated

Question 22

receptor-mediated endocytosis

Answer 22

receptor with cargo binds membrane, membrane folds in and releases vesicle via dynamin pinching off