vesicular trafficking Flashcards
anterograde pathway
moving forward through secretory pathway
retrograde pathway
moving backwards
movement of vesicles to golgi is controlled by
mediated by cytoskeleton - microtubules
bud from trans-golgi network and fuse with PM
how is cargo packaged into vesicles
- Vesicles are targeted with high fidelity to their destination
- cargo of vesicles buds off donor membrane (ER) and fuses with acceptor compartment (golgi)
protein requirements for vesicle formation
- GTPase
- adaptor protein
- recognises cargo
- coat protein
- clathrin
function of COP1 protein
COP I proteins mediate a retrograde transport pathway that selectively recycles proteins from the cis-Golgi complex to the ER.
function of COP2 protein
COP II proteins are required for selective export of newly synthesized proteins from the endoplasmic reticulum (ER)
function of small GTPases
act as molecular switches
what Guanine state does an active molecular switch have bound
- GTP = active
what Guanine state does an inactive molecular switch have bound
GDP = inactive
what molecule switches ON molecular switches
switch ON using guaning nucleotide exchange factors (GEF)
what molecule switches OFF molecular switches
switch OFF using GTPase activating proteins (GAP)
what does Ras do to signalling pathways
Ras → causes hyperactivation of signalling pathways
what is Ran protein
- GTP-binding nuclear protein
- essential for RNA and protein translocation through nuclear pore
function of COPII
allows vesicles to travel through nuclear pore
what is the GTPase allowing COPII formation
GTPase = sar1 (Arf)
what adaptor protein supports COPII coating of vesicles
sec23/24
what is the copII coat
sec13/31
role of sec24 in vesicular transport
recognises signal from receptor and binds to cargo
formation of copII coated vesicle
- cargo is recognised by adaptor (connects things) and recruits coat
- sec 24 recognises signal from receptor
- activation of sar 1 - sec 23 binds to receptor, sec 24 binds to cargo
- exit signal on cargo
- coat acts as physical structure allowing buds to form
- when bud is formed = pinches off to form vesicle
how to establish, experimentally, the minimal components required for COPII formation
- homogenise cells, break open, vesiculise
- remove ER membranes
- ribophorin = known ER membrane - ER membranes centrifuged = pellet at specific suc conc, vessicles pellet at different conc
- ran fractions on gel
role of snares in vesicular fusion
- snares wind up to make alphahelical bundle and recruit the vesicles
- vesicle has to be uncoated to allow fusion
what recruits adaptor protein
Sec23 acts as a GAP for Sar1
effect of sartGDP expression on COPII formation
inhibitory
