L2 - Vesicle tethering,docking and fusion Flashcards
(13 cards)
3 main steps innvesicle recognition and fusion
- Tethering:
specific vesicles captured by tether proteins - Docking:
SNARE proteins on vesicle + target bind - Fusion:
compartments join/fuse
what are commonly found on the surface of vesicles
different Rab-GTPAses
= Rab1 in high conc on golgi
= Rab5 on lysosomes
how many different Rab-GTPases are there
40 = help specificy where a vesicle binds
what is tethering
grabbing/capture of a vesucle by the target membrane
= controlled by tether proteins + protein complexes
= Rab proteins are of the the target for these proteins
which step are SNARE proteins crucial for
docking
= SNARE on vesicle + target membrane
= v-SNARE + t-SNARE
whata are tether factors
long coiled-coil proteins
form multi-subunit tethering complexes
= different tethers at different organelles/stages eof pathwats = helps control targetting of vesicle for specific compartments
= involved in 1st step of 2 vesicles coming together
using Rab1 as an example describe tethering
- Rab1 on golgi membrane phosphorylated –> active
- recruitsb long coiled-coil protein
- Coiled-coil interacts with the vesicle
= PROTEIN caot braek down and membrane exposed
- TRAPP-1 interacts with remanants of COP2 coat
= brings vesicle + target membrane close together
how many alpha helices do t-SNARE docking proteins have and why
3
= compared to v-SNARE single polypetide structure
describe simply the SNARE protein assemblyn in docking
SNARE paiting is very specific
- v-SNARE single polypetide pairs with t-SNARE multi-protein
= pairing is specific = 2nd layer of specificity AFTER initial tether proteins
- trans-SNARE complex removes water from inbetween them
- SNARE proteins move outwards and membranes fuse
= semi-fusion –> fusion
what is the HOPS complex
heterohexmeric complex
= multi-subunit complex made of 6 subunits
= has a range of domains inckluding Rab sites/DNARE bidning sites
describe simply how the HOPS complex aids in docking/tethering
- tethering happens between 2 compartments
- HOPS binds to t + v SNARES cia Rab/SNARE binding domain
= facilitates ‘zipping’ / fusion
= pulls SNARE proteins together
- compartments fuse + HOPS dissambles from SNARE
what is the protein NSF able to do
unwind v + t SNAREs
= allows recycling and reuse of SNAREs for new vesicles AND frees up t-SNAREs
= for incoming compartments
name the protein responsible for SNARE complex dissamebly
NSF
= unwinds SNAREs
