Lect. 13 - Intracell Vesicular traffic

Question 1

What 2 major functions does the coat perform?

Answer 1

concentrates select proteins in a specialized patch for transport; molds the vesicle to form basketlike lattice that deforms the membrane and gives shape to the vesicle

Question 2

make up of clatherin subunit

Answer 2

3 large and 3 small polypeptide chains that form a 3-legged structure called triskelion

Question 3

triskelion

Answer 3

assemble into a basket-like structure of hexagons and pentagons that form coated pits on the cytosolic side of membrane

Question 4

adaptor proteins on clatherin coated vesicles

Answer 4

form a second layer under the clatherin and trap various transmembrane proteins including receptors for soluble cargo

Question 5

assembly of clathrin coat

Answer 5

introduces a curvature in the membrane which leads to the formation of coated buds

Question 6

PI (phosphoinositides) role

Answer 6

can undergo rapid cycles of phosphorylation and dephosphorylation at the 3’, 4’, and 5’ positions; they control recruitment and binding of proteins to specific organelles/domains and regulate vesicle trafficking

Question 7

what part of the PIs are recognized by proteins?

Answer 7

headgroups

Question 8

dynamin

Answer 8

protein that assembles a ring around the clatherin bud; contains a PIP2 binding domain and GTPase domain

Question 9

PIP2 binding domain on dynamin

Answer 9

tethers the protein to membrane

Question 10

GTPase domain on dynamin

Answer 10

regulates rate of vesicle pinching

Question 11

pinching

Answer 11

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

Question 12

aside from forming a ring around the clathrin vesicle, what does the dynamin do?

Answer 12

recruits other proteins that distort the lipid bilayer (ex. lipid modifying enzymes)

Question 13

what chaperone is uses ATP to peel off the clathrin coat?

Answer 13

Hsp 70

Question 14

Rab proteins

Answer 14

monomeric G protein that direct vesicle to specific spots on the target membrane

Question 15

SNARE proteins

Answer 15

mediate fusion of vesicle w/ membrane

Question 16

how is specificity in targeting of vesicles achieved?

Answer 16

by surface markers on vesicles and complementary receptors on target membrane

Question 17

what regulated the activity of Rab?

Answer 17

GTP hydrolysis

Question 18

what is Rab bound to in the inactive form?

Answer 18

GDP (soluble form)

Question 19

what is Rab bound to in the active form?

Answer 19

GTP

Question 20

What keeps Rab in the inactive form?

Answer 20

binding to Rab-GDP dissociation inhibitor (GDI)

Question 21

what keeps Rab in the active form?

Answer 21

interaction w/ Rab-GEFs. tightly bound to a membrane

Question 22

Rab effectors

Answer 22

motor/tethering proteins that is present on the target membrane that the active form of Rab binds to

Question 23

Rab1

Answer 23

ER and Golgi complex

Question 24

Rab2

Answer 24

cis Goli network

Question 25

Rab3A

Answer 25

synaptic vesicles, secretory vesicles

Question 26

v-SNAREs

Answer 26

single polypeptide; found on VESICLE membrane

Question 27

t-SNAREs

Answer 27

2-3 proteins; found on TARGET membrane

Question 28

interaction b/w the v and t forms of SNAREs

Answer 28

allow them to wrap around eachother to form a bundle; lock the two membranes together

Question 29

what proteins are packaged into COPII?

Answer 29

newly synthesized

Question 30

where do COPII coated transport vesicles bud off from?

Answer 30

from the ER exit sites

Question 31

what chaperones are involved in misfolded proteins to keep them retained in the ER

Answer 31

BiP or calnexin

Question 32

homotypic

Answer 32

fusion of vesicles from SAME compartment

Question 33

heterotypic

Answer 33

fusion of vesicles from DIFFERENT compartments

Question 34

vesicular tubular clusters

Answer 34

fused structures resulting from vesicles that have released from the ER and fused

Question 35

COPI

Answer 35

vesicular tubular clusters bud off to form smaller vesicles that are coated w/ COPI to return proteins to the ER

Question 36

what is the retrieval pathway dependent upon?

Answer 36

ER retrieval signals

Question 37

what is the retreival sequence present in the ER membrane?

Answer 37

KKXX sequence

Question 38

what is the retrieval sequence present in soluble proteins?

Answer 38

KDEL sequence

Question 39

KKXX signal

Answer 39

interacts w/ COPI and packaged into COPI-coated vesicles

Question 40

What is needed for soluble proteins to package them into COPI-coated vesicles?

Answer 40

KDEL receptor

Question 41

golgi apparatus

Answer 41

collection of flattened, membrane-enclosed compartment (cisternae); plays important role in protein glycosylation; each golgi stack has 2 faces: cis/entry and trans/exit

Question 42

Cis Golgi Network (CGN)

Answer 42

network of fused vesicular tubular clusters arriving from ER. Proteins and lipids enter Golgi via CGN

Question 43

Trans Golgi Network (TGN)

Answer 43

region that allows exit of proteins and lipids to next step of secretory pathway

Question 44

which face of the golgi apparatus is closer to the ER?

Answer 44

cis face