SNARE regulatory proteins Flashcards

1
Q

what are SM proteins?

A

proteins whihcbintercat with syntaxin and SNARE pins

-are essential for membrane fusion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is the shape of SM protein?

A

horseshoe shape

- 4 isoforms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what does Munc 18 do?

A

It is the binding partner for syntaxin (closed)

  • bind to closed syntaxin to stop it from forming an unproductive SNARE complex
  • negative regulator of secretion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How many binding sites are thought to be on munc18?

A

2.

  • one binds to closed syntaxin and keeps closed
  • one binds to open syntaxin - form SNARE
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Is munc 18 required for vesicle fusion and how do we know this?

A
  • yes
  • when munc 18 is not present in artificial vesicles - rate of fusion is slow
  • when munc18 pre-incubated then warmed up in artifical vesicles - fusion occurs at a quicker rate
  • munc 18 is facilitating fusion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how can artificial vesicles be used to see if fusion is occuring?

A
  • one vesicle contains flourescent material (cargo) and when the vesicles fuse this flouresence is quenched

(flouresence in quenching (t-vesicle) measured at % of maximum )

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what happens in mouse chromaffin cells when munc-18 is knocked out?

A
  • is no fusion of vesicles
  • when munc-18 is re-expressed by a viral vector fusion is fully restored
  • total number of vesicles normal - but proportion of docked vesicles is reduced
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what does overexpression of SNAP-25 do in munc-18 KO chromaffin mouse cells?

A

-SNAP-25 rescues docking of vesicles but does not rescue fusion - shows that munc-18 still required for fusion to occur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is munc-13 required for?

A

fusion of glutamatergic synaptic vesicles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what happens in a munc-13 KO?

A
  • no glutamatergic transmission
  • readily releasable pool of vesicles depleted
  • vesicles can dock but cannot fuse
  • munc must have a function in between docking and fusion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what does munc 13 do to syntaxin?

A

Munc 13 can open “closed” syntaxin which promotes SNARE complex formation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what part of SNAREs form binding sites for sm proteins?

A

helixes facing outside of SNARE motif form binding sites for sm proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly