nuclear transport

Question 1

what are the 2 types of nuclear signals and their purposes

Answer 1

nuclear localisation signal (NLS) for nuclear import

nuclear export signal (NES) for nuclear export

Question 2

how can the NLS be tested

Answer 2

adding it to a protein not usually transported into nucleus/ mutating it, can be visualised with gold nanoparticles

Question 3

another word for nuclear transport receptors

Answer 3

karyopherins

Question 4

the two types of nuclear transport receptor

Answer 4

importin alpha/beta contain NLS

CRM1 exportin is an export factor for NES

Question 5

what happens when RanGDP enters the nucleus

Answer 5

it is phosphorylated into RanGTP which binds to importin and releases cargo

Question 6

what happens when RanGTP is exported to the cytosol

Answer 6

it leaves the nucleus with importin, it is then hydrolysed to RanGTP and importin is recycled to pick up more cargo

Question 7

how do the complexes enter/leave the nucleus

Answer 7

via the NPC (nuclear pore complex)

Question 8

what is the NLS and its structure

Answer 8

short basic amino acid sequence (lysine and arginines)

tags a protein for nuclear import

Question 9

what is the NES and its structure

Answer 9

tags protein for export

4 hydrophobic residues in short peptide sequence (leucine)

Question 10

why can transport receptors pass through the NPC

Answer 10

they have hydrophobic regions that allow them to pass through the gel structure of the NPC