L9-10 Protein Translocation

Question 1

What are the different coat proteins?

Answer 1

CopI
CopII
Clathrin

Question 2

What is signal sequence?

Answer 2

Hydrophobic sequence of aa on protein.

Can be in n terminus, and cleaved off by signal peptidase once sorting is complete

Or it may be in the middle of protein and stay a part of the protein

Question 3

What form of transport moves proteins in and out of nucleus?

Answer 3

Gated transport

Question 4

What does a protein need to have in order to move through the nuclear envelope?

Answer 4

Nuclear locAlisation signals

Question 5

3 main components of the nuclear pore complex?

Answer 5

Column structure
Annular subunit
Lumeneal subunit

Question 6

What does Ran-GAP do?

Answer 6

It hydrolysis (gtp to gdp) nuclear export receptor and protein (cargo) to release it in the nucleus

Question 7

What does Ran-GEF do?

Answer 7

Removes GDP and replaces with GTP on ran.

Helps ran-GTP bind to nuclear import receptor to release protein in nucleus

Question 8

Mitochondria translation complexes?

Answer 8

TOM
SAM
TIM22
TIM23

Question 9

Diff b/w TIM22 and TIM23?

Answer 9

Tim23 is in inner membrane but translocation proteins from inner membrane to matrix

Tim22 is in inner membrane but helps in insertion of protein into membrane

Question 10

What does COPII do?

Answer 10

Secretes from ER
Secretory pathway

Goes in the direction towards membrane

Question 11

What does COPI do?

Answer 11

Secretes from Golgi

Goes back to ER or back to Golgi

Question 12

What happens if a protein is continuously mis folded?

Answer 12

It is fed back into the cytosol, tagged with ubiquitin, and recognised by proteosome, which destroys it into smaller segments which can be reused

Question 13

What is a guy an structure?

Answer 13

Joined to protein containing NXT or NXS, by sugar transferase

It acts as a quality stamp

Question 14

How is glycan modified during ER quality control?

Answer 14

Glycan is trimmed, and is folded with a chaperone which fits the glycan group.
Glucosyl transferase checks if any hydrophobic regions are exposed. If yes, it’s sent back, glycan is out back in and sent back to chaperone.

Question 15

Describe how coating occurs with COPII

Answer 15

Sar1-GDP activated by SAR1-GEF (gdp to gtp)

It binds to membrane which recruits coat proteins which bind to cargo and form a vesicle.

Question 16

Describe the fusion of vesicle to target membrane.

Answer 16

Vesicle membrane contains rab proteins, which recognises rab effector on target membrane.

V snare in vesicle surface intertwined with t snare on membrane and pulls vesicle closer to the membrane.

Membranes fuse.

Question 17

What’s Kdel

Answer 17

A receptor which tells that the protein is in the wrong place. When binding to receptor, COP1 vesicle forms. Back to ER!