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Ochem > 8.11-8.17 > Flashcards

8.11-8.17 Flashcards

(64 cards)

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1
Q

the Rab/Ypt family are ___________________

A

monomeric GTPases

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2
Q

GDP-bound form of Rab is where?

A

cytosolic

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3
Q

GTP-bound form of Rab

A

IMP with C-terminal anchor of 2 phenyl (geranylgeranyl) chains

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4
Q

Rab-GDP exists in the cytosol complexed with what?

A

GDI (guanine nucleotide dissociation inhibitor)

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5
Q

what happens when Rab-GDP associated with GDI

A

phenyl group sequestered, Rab prevented from being IMP

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6
Q

what happens when Rab gets to proper donor membrane

A

GDI is released, membrane-bound Rab-GEF helps it exchange GDP for GTP, Rab-GTP gets incorporated into membrane of budding vesicle

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7
Q

function of Rab-GTP

A

works with tethers to target vesicle to acceptor membrane

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8
Q

Rab-GAP

A

helps Rab hydrolyze GTP to GDP

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9
Q

what happens after Rab-GAP works

A

GDI extracts Rab-GDP and recycles it to cytosol

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10
Q

Rab effectors

A

various tethers/fibrous coiled coil proteins that bound-Rab-GTP binds to

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11
Q

what is docking mediated by

A

SNARE proteins

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12
Q

true or false: SNAREs are specific

A

true

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13
Q

structure of SNARES

A

IMPS: t-IMP or acyl/prenyl-anchored IMP

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14
Q

how are SNARE pairs formed

A

N-terminal cytoplasmic domains form coiled-coils with cognate SNAREs

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15
Q

interaction of SNAREs in SNARE pair

A

single v-SNARE helix with three t-SNARE helices (one heavy, two light chains)

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16
Q

what is unraveling of SNARE pairs catalyzed by

A

NSF (cytosolic ATPase - forms a barrel)

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17
Q

how does NSF bind indirectly to SNAREs

A

through SNAPS - soluble NSF attachment proteins

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18
Q

triskelion

A

3-legged structure form by clathrin coat structures

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19
Q

what does each leg consist of in triskelion

A

one heavy and one light chain of clathrin

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20
Q

what kind of lattices to clathrin cages contain?

A

hexagonal and pentagonal

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21
Q

each side of hexagon or pentagon consists of what?

A

4 legs of different triskelions

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22
Q

hexagonal lattices are ______

A

flat

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23
Q

pentagonal lattices are _______

A

curved

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24
Q

what do adaptor complexes attach

A

clathrin to membrane

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25
what type of energy does scission require?
GTP energy and GTPase dynamin
26
dynamin
wraps around neck of coated pit, may constrict following GTP hydrolysis - releases clathrin-coated vesicles from pm
27
how was function of dynamic elucidated
shibire Drosophila mutation - long necks at restrictive temperature
28
what does uncoating of clathrin coat involve
hsp70-type of "uncoating ATPase" and auxilin
29
some of adaptors are part of which family?
AP family
30
AP-2 binds to what?
phosphatidylinostiol-4,5-bisphosphate - clathrin-coated pit
31
where is AP-3 present
early endosome and on
32
where is AP-1 present
late endosome and on
33
structure of adaptors
heterotetratmers with trunk domain that interacts with PM receptors and ear on hinge that interacts with clathrin and accessory proteins
34
what happens to adaptors during coat assembly
phosphorylated
35
what happens to adaptors when they are phsophorylated
expose binding sites for phosphoinositides and cytoplasmic tails of PM receptors
36
types of cytoplasmic signals of cargo proteins
tyrosine or dileucine-based
37
within 1 min of coated vesicle formation, what occurs?
scission and removal of clathrin coat
38
where does once-clathrin-coated vesicle go?
early endosome
39
how is the tethering, docking, and fusion of uncoated vesicles with the early endosome similar for both endo/exocytic pathways?
requires Rabs, tethers, and SNAREs
40
2 main scenarios for internalized receptors and ligands
1. internalized receptors discharged ligands in early endosomes, receptor is recycled, ligand moves on 2. internalized receptors + ligands move together to lysosomes
41
transferrin receptor
1. iron complexed with transferrin carried into cell 2. separated in early endosome 3. iron goes to cytoplasm 4. apotransferring returns to membrane
42
LDL receptor
1. LDL later degraded in late endosome or lysosome 2. receptor recycled back to PM
43
insulin (EGF) receptor
1. down regulation of receptor 2. both move to lysosome for degradation
44
multi vesicular bodies
late endosomes with internal vesicles
45
true or false: transport of vesicles is involved in maturation process from early endosome to lysosome
false
46
loss of receptors (recycling) converts early endosomes to what?
late endosomes
47
transport vesicles with lysosomal enzymes and membrane components come from ________ and fuse with _______________
TGN, late endosomes
48
what do early endosomes bind to?
microtubule tracks
49
where are early endosomes translocated to
center of cell - accumulate in perinuclear cytoplasm next to microtubule organizing center
50
how do MVBs ensure receptor downregulation
- receptor marked with ubiquitin by ubiquitin ligase - ubiquitin removed before selective inclusion into vesicle - degradation
51
where are soluble lysosomal enzymes and lysosomal t-IMPs translated?
ER
52
signal for proteins going to lysosome
M6P - mannose-6-phosphate
53
where is M6P signal technically generated
Golgi (TGN)
54
is M6P signal lumenal or cytoplasmic
lumenal
55
what adds the M6P signal added to terminal mannose residues by?
phosphotransferase
56
signal for M6P addition
signal patch formed when protein folding brings together non-contiguous amino acids
57
where are M6P receptors
TGN
58
steps of generating M6P signal
1. N-linked glycosylation in ER 2. CGN: GlcNAc-phosphate added by phosphotranfersase 3. TGN: GlcNAc removed exposing signal, M6P binds to receptor
59
signals on cytoplasmic tails of M6P receptors
1. tyrosine - recognized by AP-1 clathrin complexes 2. dileucine - interacts with GGA
60
what does GGA stand for
Golgi / y-adaptin / ARF
61
what happens with GGA after recognition
hands over M6P receptor and clathrin to AP-1 complex on vesicle
62
true or false: lysosomal enzymes inactive at higher pH
true
63
how are proenzyme lysosomal enzymes activated
proteolytic cleavage (but autocatalytically activated at proper pH)
64
role of phosphatases in lysosome
cleave M6P sorting signal to prevent retrograde transport to TGN

Ochem (22 decks)

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