L1 - Trafficking between ER + Golgi Flashcards
(24 cards)
what is the sorting network
slects cargo and packagae sthem into correct structure = send to place there needed
decsribe the enocytic pathway stages from plasma membrane
- material endocytosed into endocytic vesicle
- early endosome
- late endosome
- lysosome
describe the secretory pathway from Endoplasmic reticulum
- material from ER goes to Golgi
= from here can go to nearly any stage
- secetory vesicle to plasma membrane
- straight to plasmam mebrane without secretory vesicle
- to early endosome
- to late endosome
describe the retreival pathways
= taking a step back
what step is always involved when somthing comes from the ER
golgi apparatus
describe the golgis 3 layer structure
cis,medial and trans
cis = inner-most layer
medial = middle
Trans = outer most layer
how are vesicles generated
membrane budding/bending creates vesicles
= molecular motors then move the vesicles
3 steps in moving materual between compartments
budding
transport
fusion
what pathway is the membrane coat COP1 involved in
retrieval
what pathway is the membrane coat COP2 involved in
secretory
= ER outwards
describe the formation of curvature for a COP2 coat - secretory
- Sec12 GEF actiavtes Sar1
= guanine exchange factor turn on GTPases by swapping GDP–> GTP
- Sar1 activation = amphiphatic helux exposed and inserted into ER membrane
= curvature
describe the pre-budding complex formation for COP2 FOLLOWING Sar1 activation and helix insertion
- Sec23/24 binds to inserted Sar1 helix
- Sec24 clusters cargo proteins at specific sites on membrane
= pre-budding complex
describe the roles of Sec13/14 in collection of pre-budding complexes in COP2 coat formation
- Sec13/14 heterodimer binds to outside of Sec23/24 to form OUTER COAT
= full COP2 coat is now formed
describe what happenes following FULL COAT formation in COP2
- Sar inactivated by GTP hydrolysis
= COP2 breaks down = cargo released
left with a secretory LIPID vesicle WITHOUT the coat proteins attached
how do coat proteins like Sec24 know what to export - COP2
recognise sorting motifs on membrane proteins
= cytoslic tails of transmembrane proteins have ‘export motifs’
= specifically interact with Sec24 = allows specificity of cargo selection
what does COP1 use instead of Sar1s amphiphatic helix in COP2
Arf1 - Myristoyl anchor
= Arf1 is a GTPase just like Sar1 = activation causes attachment of anchor to membrane
describe the formation of COP1 vesicles
- Arf1 activated and attaches to membrane by Myristoyl anchor
- COP1 coatomer complex binds to Arf1 and selects cargo based on ‘import’ motifs
- budded vesicle is hydrolysed = vesicle released from PROTEIN COAT COMPLEX
what do some cargo proteins have that allows movement in either direction
COP1 and COP2 motifs
name a protein that van traffic between ER and golfi and why
ERGIC-53
= contains both COP2 and cOP1 binding residues so can be transported by both
name the sequence that is responsible for ‘retrieval’ of proteins from Golfi back to ERVby COP1
= lysine,aspartic acid,glutamic acid,leucine
KDEL sequence
compare GEFs between COP2 and COP1
COP2 = Sec12
Cop1 = ARF-GEF
name the GTPases and what they contain in COP1 and COP2
COP2 = Sar1 - ampphiphatic helix)
COP1 = Arf1 - lipid anchor
name the coats in COP1 and COP2
COP2 = Sec23/24 + Sec12/13
COP1 - Coatomer
what vare the rokes of COP2 and COP1 in transport
COP2 = ER export –> outwards
COP1 = Retrogade traffic to ER from Golgi + bi-directional traffic WITHIN golgi
