Zaidi Vesicular Traffic 1

Question 1

The function of transport vesicles…

Answer 1

is to transport proteins and other biomolecules

Question 2

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

Answer 2

bud off

fuse

Question 3

Contents of a vesicle are called…

Answer 3

cargo

Question 4

Transport is…

Answer 4

directional

Question 5

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

Answer 5

vesicular transport

exchange

Question 6

Cues for incoming traffic are provided by what two things?

Answer 6

composition of the membrane, molecular markers on membrane surface

Question 7

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

Answer 7

combination of markers

Question 8

Retrieval pathways

Answer 8

return molecules to their source

Question 9

How do cells segregate proteins in to membrane domains?

Answer 9

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

Question 10

transport vesicles bud off as __ vesicles

Answer 10

coated

Question 11

What are the two major functions of the vesicle coat?

Answer 11

• 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

Question 12

The vesicular coat is discarded…

Answer 12

before the vesicle fuses with target membrane

Question 13

Name the three types of coated vesicles:

Answer 13

COPI
COPII
Clathrin-coated

Question 14

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

Answer 14

Golgi cisternae
ER
Golgi apparatus
plasma membrane

Question 15

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 __.

Answer 15

polypeptide chains

triskelion

Question 16

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

Answer 16

basket-like
hexagons
pentagons

Question 17

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

Answer 17

adaptor proteins

soluble cargo

Question 18

Describe the process of clathrin coat assembly and disassembly.

Answer 18

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

Question 19

Phosphoinositides

Phosphoinositol

Answer 19

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

a phospholipid that helps with membrane process

Question 20

slide

Answer 20

18

Question 21

Bar domains serve as

Answer 21

membrane bending proteins

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

Question 22

Dynamin:

It contains __ and __

Answer 22

protein that forms a ring around a clathrin bud

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

Question 23

Pinching

Answer 23

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

Question 24

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

Answer 24

modifying enzymes that change lipid composition

Question 25

PIP2 is degraded when … which weakens the binding of ...

Answer 25

vesicle loosens clathrin coat adaptor proteins

Question 26

HSP70

Answer 26

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

Question 27

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

Answer 27

surface markers | complementary receptors

Question 28

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

Answer 28

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

Question 29

Rabs are __ __ (~60) whose activity is regulated by ___ ___. | It cycles through __ and __ and regulates reversible assembly of complexes on the __.

Answer 29

monomeric GTPases. GTP Hydrolysis. cytosol, membrane, membrane

Question 30

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.

Answer 30

GDP, GTP GDP dissociation inhibitor GEF effectors

Question 31

Subcellular locations of Rab Proteins: Rab 1 Rab 3a Rab 5

Answer 31

ER and Golgi complex synaptic vesicles, secretory vesicles earyl endosomes, plasma membrane, clathrin-coated vesicles

Question 32

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.

Answer 32

35 complimentary V T wrap around each other forming a bundle extracellular

Question 33

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

Answer 33

1 tethering 2 docking 3 fusion

Question 34

recycling of SNAREs

Answer 34

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

Question 35

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

Answer 35

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.

Question 36

Vesicles fuse with each other after...

Answer 36

budding from the ER exit sites and shedding their coat

Question 37

Contrast Homotypic and Heterotypic

Answer 37

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

Question 38

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

Answer 38

SNAREs v and t snares vesicular tubular clusters

Question 39

Retrieval Pathway

Answer 39

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

Question 40

Compare and contrast KKXX and KDEL sequences

Answer 40

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

Question 41

Golgi Apparatus

Answer 41

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

Question 42

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.

Answer 42

Cis Golgi Network (CGN) Trans Golgi Network (TGN)