vesicle budding, fusion and trafficking

Question 1

what proteins are targetted to the ER

Answer 1

ER proteins
secreted proteins
golgi proteins
lysosomal proteins
integral plasma membrane proteins

Question 2

COP1

Answer 2

proteins primarily involved in retrograde transport through the GOLGI backwards to ER

Question 3

COP II

Answer 3

proteins involved in movement between ER and cis-golgi

Question 4

clathrin

Answer 4

anterograde transport through the golgi to the endosome, and import from the cell surface

Question 5

clathrin structure

Answer 5

made up of clathrin triskelion that has 3 heavy and 3 light chains and N terminal B propeller domain

the clathrin cage is made up of overlapping clathrin triskelelion

Question 6

clathrin triskelions

Answer 6

aggregate on membrane surface drawing out as they accumulate
form clathrin coates vesicles on membrane surface

Question 7

what happens when anough clathrin has polymerized

Answer 7

it forms a complete sphere and pinches off from membrane as it forms

Question 8

what protein is ued form help form clathrin vesicles

Answer 8

dynamin which uses GTP making GDP and Pi

Question 9

coating of COPII vesicles steps

Answer 9

1. sar 1 (GTPase) membrane binding and GTP exchange. after it does this is can embed into the membrane (has GTP)
2. COPII coat assembly
3. GTP hydrolysis by sar 1
4. coat dissasembly

Question 10

what does uncoating of COPII expose

Answer 10

v snare proteins on the cesicle that can then associate with t snare proteins on the target membrane

Question 11

snare complexes allow for

Answer 11

allow for easy membrane fusion

Question 12

sturcture of snare complexes

Answer 12

long alpha helical regions that can coil around each other resulting in a strong assocaition that pulls the two membranes into very close proximity

Question 13

steps fo vesicle docking

Answer 13

1. vesicle docking
   -rab GTPase
2. assembly of snare complexes
   -rab GTPases
   -tethering proteins
3. membrane fusion
4. dissasembly of complexes
   -SNAP
   -NSF

Question 14

SNAP

Answer 14

soluble NSF associated protein

Question 15

NSF

Answer 15

n ethylameleimide sensitive fusion

Question 16

KDEL sequence

Answer 16

lys- asp- glu-leu

soluble protiens picked up in cis golgi due to lower pH and have receptor in both COPI and COPII vesicles

Question 17

KKXX sequence

Answer 17

lys-lys-x-x
membrane proteins including KDEL receptor
the sequence faces the cytosol and binds to COPI subunits

Question 18

number of golgi in cell

Answer 18

varies with function
averages about 10-20 in animal cells
low secretory cells have only about 2-3

Question 19

functions of golgi complex

Answer 19

protein modification by glycosylation
addition of sulfate groups to the amino acid tyrosine
cleavage of protein precursors to yield mature hormone and neurotrnasmitters
synth of certain membrane lipids

Question 20

lysosomes

Answer 20

membrane bound structure containing about 40 diff enzymes

nucleases, hydrolases, lipases, sulfases

Question 21

targetting to lysosome via what

Answer 21

phosphate on sugar group of the protein

Question 22

where does phosphorylation of mannose occur

Answer 22

in cis golgi

Question 23

phosphorylation of mannose steps

Answer 23

addition of phosphorylated GlcNAc to mannose

removal of the GlcNAc

becomes M6P

Question 24

sorting to lysosomes

Answer 24

does involve a signal in the protein but the signal is not recognized by a receptor instead by a third protein

mannose 6 phosphate receptor (trans golgi) binds to mannose 6 phosphate

Question 25

where is mannose 6 phosphate identified and selected

Answer 25

in the trans golgi