Intracellular Protein Trafficking (1)

Question 1

What is a signal sequence?

Answer 1

Short sequence at N-terminus

Question 2

What is a signal patch?

Answer 2

Multiple short sequences - come together with folding

Question 3

What is the signal sequence for nuclear import?

Answer 3

Lysine and arginine-rich - positive - do not need to be at end of chain

Question 4

What is the signal sequence for mitochondrial import?

Answer 4

Amphipathic alpha helix

Question 5

What is the signal sequence for ER import?

Answer 5

Hydrophobic AAs

Question 6

How do small proteins move into the nucleus?

Answer 6

Diffusion through nuclear pores

Question 7

How do large proteins move into the nucleus?

Answer 7

Active transport through nuclear pores - via contact with nuclear pore protein complex

Question 8

What are the nuclear localisation signals?

Answer 8

Signal sequence - positive lysine and arginine residues - do not need to be at end of chain
Signal patch - 2 areas of positive AAs

Question 9

Which protein does a nuclear pore complex consist of?

Answer 9

Nucleoporins

Question 10

What is the nuclear import signal?

Answer 10

NLS

Question 11

What is the nuclear export signal?

Answer 11

Double leucine

Question 12

Which protein regulates the directionality of protein transport?

Answer 12

Ran

Question 13

What is Ran-GEF and where is it located?

Answer 13

Exchanges GDP for GTP

In nucleus

Question 14

What is Ran-GAP and where is it located?

Answer 14

Hydrolyses Ran-GTP

In cytosol

Question 15

Is protein tranlocated into nucleus folded?

Answer 15

Yes

Question 16

Is protein translocated into mitochondria folded?

Answer 16

No

Question 17

Where in the mitochondria does translocation occur?

Answer 17

Where inner and outer membranes close together

Question 18

Which enzyme cleaves the signal sequence in the mitochondrial matrix?

Answer 18

Signal peptidase

Question 19

What keeps the protein unfolded for mitochondrial translocation?

Answer 19

Cytosolic Hsp70 (ATPase)

Question 20

What prevents the protein moving back through TIM and pulls it into mitochondrion?

Answer 20

Mitochondrial Hsp70 (ATPase)

Question 21

What fold the protein in the mitochondrial matrix?

Answer 21

Hsp60

Question 22

What keeps the protein unfolded in the mitochondrial intermembrane space?

Answer 22

Chaperones

Question 23

Where is the SAM complex located?

Answer 23

Outer mitochondrial membrane

Question 24

Where is the OXA complex located?

Answer 24

Inner mitochondrial membrane