Import/export

Question 1

Barrier Layer

Answer 1

FG Nups (FG repeat)

30% of mass of NPC

Question 2

Why are FG repeats important?

Answer 2

They form a hydrodynamic (hydrophobic)radius or gate of the NPC.

Question 3

How do NPCs allow transport?

Answer 3

1. Small molecules can pass freely via diffusion.
   (cutoff is 20-40 kDa)
2. Amphiphillic proteins can interact with the FG repeats and be spontaneously imported.(spontaneous migration)
3. Facilitated Transport to move proteins.

Question 4

Karyopherins are:

Answer 4

AKA importins and exportings.

Question 5

Where are you likely to find RanGTP?

Answer 5

In the nucleus.

Question 6

True or false. NLS/NES signals are one time use only.

Answer 6

FALSE

The singals are not cleaved so they are recycled.

Question 7

How can nuclear transport be regulated?

Answer 7

Regulation can occur in terms of:

Regulation of NPC, cargo receptors, and the cargo itself.

Question 8

How can problems in nuclear transport lead to pathology?

Answer 8

1. BRCA2/p53 protein exported from cell

2. NLS upregulated for certain genes

Question 9

Where does Guanine nucleotide exchange occur in the Ran GTP cycle? What is GNE?

Answer 9

In the cytoplasm.

GDP–>GTP exchange

Question 10

Where does GTP hydrolysis occur in the Ran GTP cycle?

Answer 10

Nucleus