W13

Question 1

Name three membrane coat proteins.

Answer 1

Clathrin, COPII, and COPI

Question 2

Name the directionality FROM the ER and which membrane coat protein is involved.

Answer 2

Anterograde, COPII

Question 3

Name the directionality TO the ER and which membrane coat protein is involved.

Answer 3

Retrograde, COPI

Question 4

How is membrane curvature formed when building a COPII coat?

Answer 4

Sec12 acts as a GEF on Sar1, exchanging GDP for GTP, causing exposure of the Sar1 amphipathic helix which inserts into the ER membrane

Question 5

From membrane curvature, how is a pre-budding complex formed for COPII?

Answer 5

Sar1 recruits Sec23-Sec24 heterodimers, Sec23 binds to Sar1 and Sec24 binds to membrane cargo proteins. Transport adaptors on cargo proteins capture soluble cargo within the ER lumen and a pre-budding complex forms.

Question 6

What components make up a pre-budding complex in COPII?

Answer 6

Sar1, Sec23, Sec24, and cargo

Question 7

From a pre-budding complex, how is a vesicle formed for COPII and subsequently disassembled?

Answer 7

Sec13-Sec31 heterotetramer binds to Sec23-Sec24 and collects pre-budding complexes, leading to fission of a vesicle from the donor ER membrane in which soluble ‘bulk flow’ cargo can become trapped inside. Sec23 activates hydrolysis of GTP bound to Sar1, leading to disassembly.

Question 8

Name the GEF for COPII.

Answer 8

Sec12

Question 9

Name the GEF for COPI.

Answer 9

ARF-GEF

Question 10

Name the small GTPase for COPII.

Answer 10

Sar1 (amphipathic helix)

Question 11

Name the small GTPase for COPI.

Answer 11

Arf1 (lipid anchor)

Question 12

Name the coat for COPII.

Answer 12

Sec23-Sec24
Sec13-Sec31

Question 13

Name the coat for COPI.

Answer 13

Coatomer

Question 14

Name the GAP for COPII.

Answer 14

Sec23

Question 15

Name the GAP for COPI.

Answer 15

ARF-GAP

Question 16

What are the three steps for vesicle transport?

Answer 16

Tethering, docking, and fusion

Question 17

What are the two classes of tether factors?

Answer 17

Long coiled-coil proteins and multi-subunit tethering complexes

Question 18

Where does the multi-subunit tether TRAPPI operate?

Answer 18

From ER to Golgi

Question 19

Where does the multi-subunit tether TRAPPII operate?

Answer 19

Intra-Golgi

Question 20

Where does the multi-subunit tether HOPS operate?

Answer 20

Within endolysosomal system

Question 21

Where does the multi-subunit tether Exocyst operate?

Answer 21

Late secretory pathway at plasma membrane

Question 22

Describe the structure of NSF.

Answer 22

Hexameric AAA-ATPase

Question 23

What are the two models for movement of cargo through the Golgi?

Answer 23

Cisternal maturation model and vesicle transport model

Question 24

Describe the transport of cargo from TGN to lysosome.

Answer 24

Proteins are modified by mannose-6-phosphate and collected in clathrin coated vesicles before being transported via endosomes to lysosomes.

Question 25

Describe the transport of cargo from TGN to plasma membrane.

Answer 25

Accumulation of cargo in specific regions of TGN, default pathway

Question 26

What kind of molecules are transported for regulated secretion?

Answer 26

Neurotransmitters and signalling molecules e.g. insulin

Question 27

What opens the clathrin adaptor complex AP-2 complex?

Answer 27

Phosphoinositide PI(4,5)P2

Question 28

What is co-incidence detection?

Answer 28

Ability of clathrin adaptor complexes to recognise both PIP2 and the sorting motifs of cargo receptors

Question 29

What is dynamin’s function?

Answer 29

GTPase forms tubular polymers around clathrin triskelion to cause vesicle scission