The Cytoskeleton

Question 1

How big are actin filaments, intermediate filaments and MTs?

Answer 1

7, 10 and 25nms

Question 2

Where do MTs grow out of?

Answer 2

The MT organising centre which contains two centrioles.

Question 3

What are MTs made out of?

Answer 3

a and B tubulin dimers.

Question 4

What is the +end?

Answer 4

B-tubulin, the fast-growing end, towards the plasma membrane

Question 5

What is the -end?

Answer 5

a-tubulin, the slow-growing end, from the MTOC.

Question 6

How is tubulin post-translationally modified?

Answer 6

Detyrosination (EEY–> Y removed)
Acetylation at K40
Polyglutamylation (addition of multiple E residues)

Question 7

What adds to the +end?

Answer 7

GTP-tubulin subunits, when the GTP cap is lost the MT depolymerises (catastrophe)

Question 8

What are the motor proteins called?

Answer 8

Kinesin and Dynein

Question 9

Which motor proteins migrate to which ends?

Answer 9

Kinesin walks to the +end powered by ATP hydrolysis

Question 10

What does cytoplasmic dynein need for trafficking?

Answer 10

Dydactin

Question 11

Which viruses does dynein bind to?

Answer 11

Adenovirus, herpes and HIV-1

Question 12

which viruses does Kinesin bind to?

Answer 12

Vaccinia and herpes

Question 13

What do MAPs do?

Answer 13

Stabilise and destabilise MT to make more efficient trafficking

Question 14

Name 3 MAPs

Answer 14

Tau, MAP2 and spastin

Question 15

When does Tau detach?

Answer 15

When phosphorylated

Question 16

What is spastin?

Answer 16

A member of the AAA protein family, attaches to the C-terminal tubulin tails and dislodges them from the MT lattice stimulated by MT polyglutamylation

Question 17

What do multiple dyneins in motile cilia do?

Answer 17

cause bending

Question 18

What forms a motile cilia?

Answer 18

9 pairs of dynein + 2 in the centriole

Question 19

How do defects in Tau result in Alzheimer’s?

Answer 19

Hyperphosphorylation results in detachment, aggregation and formation of neurofibrilliary tangles.

Question 20

What is caused by mutations in spastin?

Answer 20

Spastic paraplegia, autosomal dominant, progressive lower limb spasticity and degregation of spinal neurones.

Question 21

What causes Lissencephaly?

Answer 21

Mutation in a-tubulin - smooth brain and small head.

Question 22

What do N256S abd K253N do in hereditary spastic paraplegia?

Answer 22

reduce velocity of movement

Question 23

What do R280S and K25N do in HSP?

Answer 23

Reduce binding to MTs when attached to cargo.

Question 24

What mutation causes Chacot-Marie-Tooth disease type 2A?

Answer 24

Kif1BB trafficking of mitochondria in neurones.

Question 25

What do Paclitaxel and Docetaxol do?

Answer 25

Stabilise MTs - affects cell proliferation

Question 26

What does Taxol do?

Answer 26

Induce mitotic arrest and increases the number of abnormal spindles

Question 27

What does Monastrol do?

Answer 27

Inhibits E5G which makes the MTs slide apart from the spindle

Question 28

What is affected in ciliary dyskinesia?

Answer 28

Mutations in dynein heavy chain - heart is on the right side of the chest due to missing cilia in the early embryo (no L/R gradient)