8 – Controlling Microtubules

Question 1

microtubules associated proteins that Regulate microtubule cytoskeleton
(5)

Answer 1

Polymerases – accelerate growth

Depolymerases – tear apart/break GTP cap

+TIP proteins – recognize growing end

Severing enzymes – sever

Nucleation factors – initiate birth of new microtubule

Question 2

Microtubules Predominantly nucleated by…

how do we know this

Answer 2

centrosome
-NOT cold resistance = cold = collapse
=normal temp = regrows back

Question 3

Centrosome = consist of

Answer 3

2 centrioles + pericentriolar material +
𝛾 -TURCs

Question 4

𝛾-Tubulin Ring Complexes provide…

Answer 4

provide template for microtubule nucleation

Question 5

…= drives Axon outgrowth

& what is special about it.

Answer 5

Microtubule nucleation

Because there is no 𝛾 -TURCs in growth cones!

Question 6

disease caused by …

Answer 6

Doublecortin mutation

Cause of disease = failure in neuronal migration

Question 7

Nucleation factors – initiate birth of new microtubule (2)

Answer 7

• 𝛾-TuRC – template by base=plate
  Arrange monomers
• MAPs – regulate nucleation

Question 8

Severing enzymes are…

Answer 8

ATPases – cut microtubules in the middle

Question 9

severing enzyme example

Answer 9

katanin
-big hexameric ring, has pore in the middle
1. grabs onto C terminal tail of tubulin polypeptide
2. end of protein gets threaded though the pore

Question 10

…recognize growing end

Answer 10

+TIP proteins
-Track growing microtubule ends
-Binds specifically to GTP-cap of microtubules

Question 11

actual recognition of growing end is which protein

Answer 11

EB1 - end binding protein 1
-can bind to GTP-cap
-recognize specific plus end structure

other +TIPS hitchhike on EB1

Question 12

which protein is used to trigger catastrophes

Answer 12

Depolymerases
-Remove tubulin from ends & trigger catastrophes

Question 13

depolymerase example

Answer 13

Kinesin-13 (ATP ase)

MCAK depolymerizes microtubules

Question 14

Polymerases example & function

Answer 14

XMAP215 accelerates microtubule growth – catalyst!!!

Question 15

XMAP215 binds to…

Answer 15

Binds to tubulin dimers

-Both growing & shrinkage – finds equilibrium – forward rxn accelerated

Question 16

XMAP215 catalyses … (since its a catalyst)

Answer 16

-Catalyzes reverse reaction (shrinkage) TOO

Low tubulin concentration → promotes depolymerization

High tubulin concentration → promotes polymerization

Question 17

XMAP215 can stabilize

Answer 17

a weakly-attached tubulin dimer

Question 18

Actin filaments Vs Microtubule

Nucleation

Answer 18

Arp2/3 Vs 𝛾 -TuRCs

Question 19

Actin filaments Vs Microtubule

Polymerase

Answer 19

Formin Vs XMAP215

Question 20

Actin filaments Vs Microtubule

Depolymerase

Answer 20

None Vs MCAK

Question 21

Actin filaments Vs Microtubule

+TIP proteins

Answer 21

Capping protein Vs EB1, etc

Question 22

Actin filaments Vs Microtubule

Severing enzyme

Answer 22

cofilin Vs Katanin