Nuclear transport

Question 1

Nuclear pores are made of

Answer 1

5 types of subunit, 30 proteins with a basket structure

-Annular subunit, luteal subunit, ring subunits, fibrils, nuclear basket

Question 2

mass of the nuclear pore

Answer 2

125 million dalton

Question 3

approx how many pores are there in the Nuclear envelope of a mammal

Answer 3

3000-4000 pores

Question 4

the basket structure

Answer 4

unstructured and tangled fibrils which restricts movement in the nucleas by blocking the central opening

Question 5

molecule sizes that can diffuse in and that need A transport

Answer 5

molecules smaller than 5KDa - move through freely by diffusion
molecules which are larges than 60Kda require active transport

Question 6

where is rRNA made

Answer 6

in the nucleus

Question 7

what need to get in/out of the nucleus

Answer 7

DNA in and mRNA needs to get out to be translated by the ribosomes in the cytosol

Question 8

proteins which are made for the ribosome in the nucleus

Answer 8

90 of them - collated in the nucleus - then move out through the pore

Question 9

NLS

Answer 9

nuclear localisation signal
+ve charged, 1 protein in whole complex needs to have NLS for the whole thing to be imported

rich in lysine and arginine

Question 10

NLS

Answer 10

nuclear localisation signal
+ve charged, 1 protein in whole complex needs to have NLS for the whole thing to be imported

rich in lysine and arginine

Question 11

NIR

Answer 11

nuclear import receptors - s shaped - Karyopherins

Question 12

which small GTPase is important in nuclear import

Answer 12

Ran

Question 13

GAPs

Answer 13

GTPase activting protein - inc GTP-GDP

Question 14

nuclear import where would you find more GAPs

Answer 14

in the cytosol - mainly Ran,GDP

Question 15

nuclear import where would you find more GEFs

Answer 15

in the nucleus - mainly Ran.GTP

Question 16

karyopherins wont bind

Answer 16

ran.gdp - so they are free to bind cargo

Question 17

karyopherin-cargo crosses the NPC

Answer 17

encounters RanGTP - which binds replacing the cargo and moves back across into the cytosol

Question 18

cytosol RanGTP-Karyopherin

Answer 18

encounter GAP - frees karyopherin

Question 19

RanGDP - transported back to the nucleus via

Answer 19

its own receptor and is converted back into RanGTP by GEF

Question 20

Nuclear transport occurs when

Answer 20

specific proteins interact with karyopherins in Ran.GTP manner

Question 21

how has visualising the nuclear transport been made possible

Answer 21

by coating gold particles with the NLS - and then injecting them into the cytosol - visualise then through electron microscopy

Question 22

how does macromolecular transport differ across NPC than transport of proteins across membranes

Answer 22

large aqueous pores rather than through lipid bilayer

Question 23

NPC allows

Answer 23

fully folded proteins to enter the Nucleus - squeezing them through the NPC
newly formed ribosomal subunits to exit fully assembled

Question 24

yeast have how many genes encoding karyopherins

Answer 24

14

animals have many more

Question 25

nuclear export

Answer 25

similar to nuclear import but in reverse - RanGTP in the nucleus promotes cargo binding to export receptor rather than dissociating it - cytosol - GAP hydrolyses GTP - export receptor - releases cargo in the cytosol

Question 26

during mitosis - phosphorylation of the lamins

Answer 26

break down the nuclear laminar - which breaks up the nuclear envelope

Question 27

dephospho rylation of laminar

Answer 27

reassemble the NE in clusters around decondensing chromosomes