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Ochem > 8.11-8.17 > Flashcards

8.11-8.17 Flashcards

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
Q

what type of energy does scission require?

A

GTP energy and GTPase dynamin

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26
Q

dynamin

A

wraps around neck of coated pit, may constrict following GTP hydrolysis
- releases clathrin-coated vesicles from pm

27
Q

how was function of dynamic elucidated

A

shibire Drosophila mutation - long necks at restrictive temperature

28
Q

what does uncoating of clathrin coat involve

A

hsp70-type of “uncoating ATPase” and auxilin

29
Q

some of adaptors are part of which family?

30
Q

AP-2 binds to what?

A

phosphatidylinostiol-4,5-bisphosphate
- clathrin-coated pit

31
Q

where is AP-3 present

A

early endosome and on

32
Q

where is AP-1 present

A

late endosome and on

33
Q

structure of adaptors

A

heterotetratmers with trunk domain that interacts with PM receptors and ear on hinge that interacts with clathrin and accessory proteins

34
Q

what happens to adaptors during coat assembly

A

phosphorylated

35
Q

what happens to adaptors when they are phsophorylated

A

expose binding sites for phosphoinositides and cytoplasmic tails of PM receptors

36
Q

types of cytoplasmic signals of cargo proteins

A

tyrosine or dileucine-based

37
Q

within 1 min of coated vesicle formation, what occurs?

A

scission and removal of clathrin coat

38
Q

where does once-clathrin-coated vesicle go?

A

early endosome

39
Q

how is the tethering, docking, and fusion of uncoated vesicles with the early endosome similar for both endo/exocytic pathways?

A

requires Rabs, tethers, and SNAREs

40
Q

2 main scenarios for internalized receptors and ligands

A
  1. internalized receptors discharged ligands in early endosomes, receptor is recycled, ligand moves on
  2. internalized receptors + ligands move together to lysosomes
41
Q

transferrin receptor

A
  1. iron complexed with transferrin carried into cell
  2. separated in early endosome
  3. iron goes to cytoplasm
  4. apotransferring returns to membrane
42
Q

LDL receptor

A
  1. LDL later degraded in late endosome or lysosome
  2. receptor recycled back to PM
43
Q

insulin (EGF) receptor

A
  1. down regulation of receptor
  2. both move to lysosome for degradation
44
Q

multi vesicular bodies

A

late endosomes with internal vesicles

45
Q

true or false: transport of vesicles is involved in maturation process from early endosome to lysosome

46
Q

loss of receptors (recycling) converts early endosomes to what?

A

late endosomes

47
Q

transport vesicles with lysosomal enzymes and membrane components come from ________ and fuse with _______________

A

TGN, late endosomes

48
Q

what do early endosomes bind to?

A

microtubule tracks

49
Q

where are early endosomes translocated to

A

center of cell - accumulate in perinuclear cytoplasm next to microtubule organizing center

50
Q

how do MVBs ensure receptor downregulation

A
  • receptor marked with ubiquitin by ubiquitin ligase
  • ubiquitin removed before selective inclusion into vesicle
  • degradation
51
Q

where are soluble lysosomal enzymes and lysosomal t-IMPs translated?

52
Q

signal for proteins going to lysosome

A

M6P - mannose-6-phosphate

53
Q

where is M6P signal technically generated

A

Golgi (TGN)

54
Q

is M6P signal lumenal or cytoplasmic

55
Q

what adds the M6P signal added to terminal mannose residues by?

A

phosphotransferase

56
Q

signal for M6P addition

A

signal patch formed when protein folding brings together non-contiguous amino acids

57
Q

where are M6P receptors

58
Q

steps of generating M6P signal

A
  1. N-linked glycosylation in ER
  2. CGN: GlcNAc-phosphate added by phosphotranfersase
  3. TGN: GlcNAc removed exposing signal, M6P binds to receptor
59
Q

signals on cytoplasmic tails of M6P receptors

A
  1. tyrosine - recognized by AP-1 clathrin complexes
  2. dileucine - interacts with GGA
60
Q

what does GGA stand for

A

Golgi / y-adaptin / ARF

61
Q

what happens with GGA after recognition

A

hands over M6P receptor and clathrin to AP-1 complex on vesicle

62
Q

true or false: lysosomal enzymes inactive at higher pH

63
Q

how are proenzyme lysosomal enzymes activated

A

proteolytic cleavage (but autocatalytically activated at proper pH)

64
Q

role of phosphatases in lysosome

A

cleave M6P sorting signal to prevent retrograde transport to TGN

Ochem (21 decks)

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