vesicular trafficking

Question 1

anterograde pathway

Answer 1

moving forward through secretory pathway

Question 2

retrograde pathway

Answer 2

moving backwards

Question 3

movement of vesicles to golgi is controlled by

Answer 3

mediated by cytoskeleton - microtubules
bud from trans-golgi network and fuse with PM

Question 4

how is cargo packaged into vesicles

Answer 4

• Vesicles are targeted with high fidelity to their destination
• cargo of vesicles buds off donor membrane (ER) and fuses with acceptor compartment (golgi)

Question 5

protein requirements for vesicle formation

Answer 5

• GTPase
• adaptor protein
  
  • recognises cargo
• coat protein
  
  • clathrin

Question 6

function of COP1 protein

Answer 6

COP I proteins mediate a retrograde transport pathway that selectively recycles proteins from the cis-Golgi complex to the ER.

Question 7

function of COP2 protein

Answer 7

COP II proteins are required for selective export of newly synthesized proteins from the endoplasmic reticulum (ER)

Question 8

function of small GTPases

Answer 8

act as molecular switches

Question 9

what Guanine state does an active molecular switch have bound

Answer 9

• GTP = active

Question 10

what Guanine state does an inactive molecular switch have bound

Answer 10

GDP = inactive

Question 11

what molecule switches ON molecular switches

Answer 11

switch ON using guaning nucleotide exchange factors (GEF)

Question 12

what molecule switches OFF molecular switches

Answer 12

switch OFF using GTPase activating proteins (GAP)

Question 13

what does Ras do to signalling pathways

Answer 13

Ras → causes hyperactivation of signalling pathways

Question 14

what is Ran protein

Answer 14

• GTP-binding nuclear protein
• essential for RNA and protein translocation through nuclear pore

Question 15

function of COPII

Answer 15

allows vesicles to travel through nuclear pore

Question 16

what is the GTPase allowing COPII formation

Answer 16

GTPase = sar1 (Arf)

Question 17

what adaptor protein supports COPII coating of vesicles

Answer 17

sec23/24

Question 18

what is the copII coat

Answer 18

sec13/31

Question 19

role of sec24 in vesicular transport

Answer 19

recognises signal from receptor and binds to cargo

Question 20

formation of copII coated vesicle

Answer 20

1. cargo is recognised by adaptor (connects things) and recruits coat
2. sec 24 recognises signal from receptor
3. activation of sar 1 - sec 23 binds to receptor, sec 24 binds to cargo
4. exit signal on cargo
5. coat acts as physical structure allowing buds to form
6. when bud is formed = pinches off to form vesicle

Question 21

how to establish, experimentally, the minimal components required for COPII formation

Answer 21

1. homogenise cells, break open, vesiculise
2. remove ER membranes
   - ribophorin = known ER membrane
3. ER membranes centrifuged = pellet at specific suc conc, vessicles pellet at different conc
4. ran fractions on gel

Question 22

role of snares in vesicular fusion

Answer 22

• snares wind up to make alphahelical bundle and recruit the vesicles
• vesicle has to be uncoated to allow fusion

Question 23

what recruits adaptor protein

Answer 23

Sec23 acts as a GAP for Sar1

Question 24

effect of sartGDP expression on COPII formation

Answer 24

inhibitory