L2 SNAREs 1

Question 1

What do SNAREs do

Answer 1

facilitate membrane fusion and release of the contentsof vesicles

Question 2

Which steps offusion are SNAREs required in

Answer 2

all of the steps

Question 3

What are the 3 main SNAREs and where are they

Answer 3

VAMP - on the vesicle

SNAP25 and Syntaxin on the other membrane

Question 4

List 5 physio systems that use vesicle fusion

Answer 4

1. Neurons - neurotransmitters
2. Secretory granules - endocrine and exocrine functions of the pancreas(secreting and insulin)
3. Secretion of serum proteins (albumin from hepatocytes and antibodies from plasma cells)
4. Mucus secretion (epithelial mucosal cells)
5. Intracellular transport of proteins between organelles in all cells

Question 5

Golgi function

Answer 5

Protein sorting and packaging into secretory vesicles

Question 6

3 pathways for proteins from the Golgi

Answer 6

1. Regulated secretory pathway
2. Constitutive (unregulated) secretory pathway
3. Signal-mediated diversion to lysosomes (via endosomes)

Question 7

Requirements for the regulated secretory pathway

Answer 7

• A signal has to be released and stimuate the release
• Regulatedby intracellular secretory pathways
  = Used for signals like hormones and neurottransmitters

Question 8

How was NSF discovered

Answer 8

N-ethylmaleimidie was found to ibhibit the rate of transport. NSF was the protein targeted by NEM

Question 9

What is NSF

Answer 9

N-ethylmaleimide Sensitive Factor - an ATP-ase

Question 10

What does SEC 1 encode

Answer 10

SNARE binding protein

Question 11

What does SEC 17 encode

Answer 11

alpha-SNAP

Question 12

What does SEC 18 encode

Answer 12

NSF

Question 13

Pacific Electric Ray neuron pros

Answer 13

very big neurons

Question 14

What is Rothman’s SNARE hypothesis

Answer 14

1. There are SNAREs for each step of transport within the cell
2. SNAREs should provide specificity to vesicle transport
3. SNAREs should be sufficient to drive lipid bilayer fusion
4. Proposed that NSF and ATP hydrolysis catalyses the membrane fusion - THIS IS WRONG

Question 15

What is the shape of the neuronal SNARE complex

Answer 15

Parallel coiled coil

Question 16

NSF function

Answer 16

unzipping the SNARE complex after membrane fusion

Question 17

Is NSF required for fusion

Answer 17

No, only for unzipping

Question 18

Why are SNAREs important

Answer 18

Membranes are both hydrophobic and charged, so it is energetically unfavourable for them to fuse - SNAREs provide the energy for fusion

Question 19

Ratio of R and Q snares

Answer 19

3Q:1R

Question 20

What would a mutation in one of the Q/R components do

Answer 20

Inhibit the function of the whole complex

Question 21

How specific are SNAREs

Answer 21

• Fuse only with SNAREs with the correct Q:R ratio

- A bit promiscuous but generally interact with SNAREs from appropriate membranes

Question 22

Common features of SNARE proteins

Answer 22

Conserved topology:

generally small, anchored by the C-terminal and have at least 1 SNARE motif

Question 23

Are SNAREs sufficient for membrane fusion?

Answer 23

Yes, but it occurs VERY slowly (almost no fusion)

Ca2+ enhances the rate of fusion

Question 24

What is teh extended part of syntaxin and what does it do

Answer 24

It’sthe regulatory part of the protein - if cut off, vesicle fusion won’thappen

Question 25

What does NSF use for unzipping

Answer 25

It uses its ATP-ase activity