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MCB - Dr. Zaidi > Zaidi Vesicular Traffic 1 > Flashcards

Zaidi Vesicular Traffic 1 Flashcards

1
Q

The function of transport vesicles…

A

is to transport proteins and other biomolecules

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2
Q

Vesicles __ __ from primary compartment and __ with the next one.

A

bud off

fuse

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3
Q

Contents of a vesicle are called…

A

cargo

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4
Q

Transport is…

A

directional

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5
Q

__ mediates a continuous __ of components between various membrane enclosed compartments.

A

vesicular transport

exchange

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6
Q

Cues for incoming traffic are provided by what two things?

A

composition of the membrane, molecular markers on membrane surface

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7
Q

Like a zip code, __ of __ gives each compartment its full molecular address.

A

combination of markers

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8
Q

Retrieval pathways

A

return molecules to their source

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9
Q

How do cells segregate proteins in to membrane domains?

A

By assembling a special coat on the cytosolic side of the membrane.

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10
Q

transport vesicles bud off as __ vesicles

A

coated

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11
Q

What are the two major functions of the vesicle coat?

A
  • concentrates select proteins in a specialized patch for transport.
  • coat molds the vesicle to form a basket like lattice that deforms the membrane and gives shape to the vesicle
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12
Q

The vesicular coat is discarded…

A

before the vesicle fuses with target membrane

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13
Q

Name the three types of coated vesicles:

A

COPI
COPII
Clathrin-coated

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14
Q

COPI vesicles mediate transport from the __ __, while COPII mediates transport from the __. Clathrin coated vesicles mediate transport from __ __ and from __ __.

A

Golgi cisternae
ER
Golgi apparatus
plasma membrane

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15
Q

The major protein of clathrin-coated vesicles is __.

Each clathrin subunit contains 3 large and 3 small ___ ___ that form a 3 legged structure called a __.

A

polypeptide chains

triskelion

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16
Q

Triskelions assemble into __-__ structure of __ and __ that form coated pits on the cytosolic side of the membrane.

A

basket-like
hexagons
pentagons

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17
Q

The second layer between the cage and the membrane of clathrin coated vesicles is formed by…
These proteins trap various transmembrane proteins including receptors that capture ___ ___ inside vesicle

A

adaptor proteins

soluble cargo

18
Q

Describe the process of clathrin coat assembly and disassembly.

A

1 assembly of coat protein molecules introduces a curvature in the membrane.
2 leads to the formation of coated buds.
3 adaptor proteins bind clathrin and membrane-bound cargo receptors.
4 selective recruitment of membrane and cargo molecules in vesicle.
5 clathrin coat lost after vesicle formation completed

19
Q

Phosphoinositides

Phosphoinositol

A

play a major role in coat assembly, vesicle formation, and protein trafficking

a phospholipid that helps with membrane process

20
Q

slide

A

18

21
Q

Bar domains serve as

A

membrane bending proteins

(coil-like proteins) coiled coils which dimerize into domains

22
Q

Dynamin:

It contains __ and __

A

protein that forms a ring around a clathrin bud

PIP2 binding domain (tethers the protein to membrane) and GTPase domain (regulates rate of pinching)

23
Q

Pinching

A

brings the 2 cytosolic sides of the membrane closer together and allows them to fuse

24
Q

Proteins recruited by dynamin to distort the lipid layer do so by

A

modifying enzymes that change lipid composition

25
Q

PIP2 is degraded when … which weakens the binding of …

A

vesicle loosens clathrin coat

adaptor proteins

26
Q

HSP70

A

chaperone protein that peels off clathrin coat with the use of ATP

27
Q

specificity is achieved by what on vesicles and what on target membrane?

A

surface markers

complementary receptors

28
Q

What two proteins play a role in specificity? What are the functions of each?

A

Rab proteins- direct vesicle to specific spots on target membrane
SNARE proteins- mediate fusion of vesicle with membrane

29
Q

Rabs are __ __ (~60) whose activity is regulated by ___ ___.

It cycles through __ and __ and regulates reversible assembly of complexes on the __.

A

monomeric GTPases.
GTP Hydrolysis.

cytosol, membrane, membrane

30
Q

Rab is inactive in the ___-bound form and active in the __-bound form.

Binding with Rab-__ __ __ keeps it in the inactive GDP-bound form that is soluble.

Interaction with Rab-__ keeps it in an active GTP- bound form tightly bound to a membrane.
The active form binds to Rab ___ (motor proteins or tethering proteins) present in the target membrane.

A

GDP, GTP

GDP dissociation inhibitor

GEF

effectors

31
Q

Subcellular locations of Rab Proteins:

Rab 1

Rab 3a

Rab 5

A

ER and Golgi complex

synaptic vesicles, secretory vesicles

earyl endosomes, plasma membrane, clathrin-coated vesicles

32
Q

there are # different SNARE Proteins, each associated with a different compartment.

They exist as ___ sets.

__-snares (single polypeptide) are found on vesicle membrane

__-snares (2-3 proteins) are found on target membranes

Interaction between the two forms of snares allows them to … which locks the 2 membranes together.

Fusion may be triggered by specific ___ signals which may remove inhibitory signals which may remove inhibitory proteins that prevent complete fusion.

A

35

complimentary

V

T

wrap around each other forming a bundle

extracellular

33
Q

What are the three steps of docking and fusion of a vesicle?

A

1 tethering
2 docking
3 fusion

34
Q

recycling of SNAREs

A

SNAREs are detangled by NSF which utilize ATP to separate SNAREs to make them available for another capture

35
Q

Newly synthesized proteins are packaged into __ __ transport vesicles which bud off from ER __ __.

Proteins display __ __ on their cytolsolic surface which are recognized by receptors present on the __ coat.

Describe Quality control

A

COPII coated
Exit sites

exit signals
COPII

Incompletely folded or misfolded proteins are retained in ER by bindinig to chaperone proteins such as BiP or calnexin and are degraded.

36
Q

Vesicles fuse with each other after…

A

budding from the ER exit sites and shedding their coat

37
Q

Contrast Homotypic and Heterotypic

A

Fusion of vesicles from same compartment versus fusion of vesicles from different compartments.

38
Q

Fusion of vesicles requires ___, with both membranes contributing _- and _-____ to form…

A

SNAREs
v and t snares
vesicular tubular clusters

39
Q

Retrieval Pathway

A

Process for returning proteins to ER from Golgi based on ER retrieval signals.
Large vesicles bud off to form smaller vesicles coated with COPI.

40
Q

Compare and contrast KKXX and KDEL sequences

A

Both are ER retrieval signals that are packaged into COPI coated vesicles

KKXX is present in ER membrane proteins, interacts with COPI

KDEL is present in soluble proteins that require a KDEL receptor to be packed into COPI vesicles

41
Q

Golgi Apparatus

A

Collection of flattened, membrane-enclosed compartments called cisternae.
2 faces: cis (entry) and trans (exit)
Plays an important role in glycosylation

42
Q

The ______ is a network of fused vesicular tubular clusters arriving from the ER. Proteins and lipids enter Golgi via this.

The _____ is the region that allows exit proteins and lipids to next step of secretory pathway.

A

Cis Golgi Network (CGN)

Trans Golgi Network (TGN)

MCB - Dr. Zaidi (12 decks)

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