L6 - SNARES Flashcards
what are the 6 steps in membrane fusion?
1- tethering 2- docking 3- fusion initiation 4- hemifusion (pore not open) 5- fusion pore opening 6- fill collapse
what does SNARE stand for?
SNAp REceptor
what are the purpose of SNARES?
they facilitate membrane fusion
what do V-SNAREs do?
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
what does SNAP stand for?
Soluble Nsf Attachment Protein
What is NSF?
N-ethylmaleimide- sensitive fusion protien
Sec18
what is required for ER to Golgu transport?
Sec17
What must happen before NSF can bind?
SNAP must be bound to SNAREs before NSF can bind
What do NSF-SNAP-SNARE form?
Forms a stable 20s complex (requires ATP hydrolysis of NSF to dissociate)
when were the first mammalian SNAREs discovered, and by who?
1993, J Rothman lab identified first mammalian snares
What were the first identified mammlain SNARES?
- 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)
What forms 7S complex?
One V-SNARE coil - (synaptobrevin)
Three T- SNARE coils (2 from SNAP-25, 1 from syntaxin)
what binds to the 7S complex?
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)
What is NSF required for?
- 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
Give the conserved structure of SNARE proteins
- common motifs are conserved
- all have conserved SNARE MOTIF (SNAP-25 has 2 SNARE motifs)
