Membrane Fusion Flashcards
Why is it important to regulate membrane fusion?
Highly ineffecient process
- must overcome repulsive forces
Needs machinery to make process as effecient as possible
Want specificity to ensure only the right molecules enter - and they go to the right place
What are SNAREs?
soluble NSF attachment protein receptors
-soluble proteins that help transport vesicles fuse with target membranes
What are the 3 main classes of SNAREs?
- syntaxins
- VAMPs (Vesicle associated membrane proteins)
- SNAPs (soluble NSF attachment protein/ synaptosome associated protein)
Where is VAMP located?
in transport vesicle
Where are syntaxin and SNAPs located?
in target membrane
What does NSF do?
recycle SNAP -> disassemble SNARE complex for reuse
What does Sec1 do?
after SNARE disassembled -> sec1 binds and changes syntaxin into the active confirmation
How are transport vesicles delivered to the fusion site?
molecular motor proteins move the vesicle along actin or microtubule tracks
What class of viruses undergoes membrane fusion in order to infect cells?
Envelope viruses:
HIV
ebola
influenza
How do envelope viruses enter membranes?
mimic SNAREs
- efficient
- specific
Specialized viral fusion proteins:
transmembrane domain
highly hydrophobic fusion domain (hidden until pH change or another signal)
What happens when the viral highly hydrophobic fusion domain of a virus is exposed?
it is inserted into targets cell membrane -> refolding of fusion protein leading to fusion of viral and cellular membrane
What does botulism toxin do?
prevent membrane fusion by cleaving SNARE proteins
What does a snare complex look like?
3Q’s: 1R
Q: syntaxin/ SNAPS
R: VAMP
