L6 - SNARES Flashcards

1
Q

what are the 6 steps in membrane fusion?

A
1- tethering
2- docking
3- fusion initiation
4- hemifusion (pore not open)
5- fusion pore opening
6- fill collapse
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2
Q

what does SNARE stand for?

A

SNAp REceptor

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3
Q

what are the purpose of SNARES?

A

they facilitate membrane fusion

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4
Q

what do V-SNAREs do?

A

Each class of transport vesicle contains a V-SNARE (a targeting protein) which can associate with a receptor protein (T-SNARE) which is specifc to the acceptor membrane

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5
Q

what does SNAP stand for?

A

Soluble Nsf Attachment Protein

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6
Q

What is NSF?

A

N-ethylmaleimide- sensitive fusion protien

Sec18

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7
Q

what is required for ER to Golgu transport?

A

Sec17

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8
Q

What must happen before NSF can bind?

A

SNAP must be bound to SNAREs before NSF can bind

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9
Q

What do NSF-SNAP-SNARE form?

A

Forms a stable 20s complex (requires ATP hydrolysis of NSF to dissociate)

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10
Q

when were the first mammalian SNAREs discovered, and by who?

A

1993, J Rothman lab identified first mammalian snares

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11
Q

What were the first identified mammlain SNARES?

A
  • brain specific synaptic proteins
  • syntaxin A+B
  • SNAP-25
  • VAMP/synaptobrevin 2 (lightest)

(have different bands on western blot - how know are 2 syntaxins (B heavier (heaviest/largest) than A)

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12
Q

What forms 7S complex?

A

One V-SNARE coil - (synaptobrevin)

Three T- SNARE coils (2 from SNAP-25, 1 from syntaxin)

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13
Q

what binds to the 7S complex?

A

SNAP and NSF bind to 7S complex (SNARES) to from 20S complex.

(series of protein-protein interactions occur to form stable 20s complex-required for docking and membrane fusion)

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14
Q

What is NSF required for?

A
  • NSF was originally thought to be required for vesicle fusion - but this was incorrect
  • NSF hydrolysis is required for dissociaiton of trans and cis SNARE complexes which regenerates free SNAREs for next round of docking/fusion
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15
Q

Give the conserved structure of SNARE proteins

A
  • common motifs are conserved

- all have conserved SNARE MOTIF (SNAP-25 has 2 SNARE motifs)

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16
Q

what creates acceptor site for synaptobrevin2/VAMP?

A

snap 25 and syntaxin dimer (3 snare motifs) creates acceptor complex for vesicular synaptobrevin

17
Q

How many SNARE motifs are in 7s complex?

A

4

  • 2 from SNAP25
  • 1 from synaptobrevin (vesicular)
  • 1 from syntaxin