Stuff I need to learn

Question 1

Within the centrosomes from what do microtubules nucleate?

Answer 1

The gamma tubulin ring

Question 2

What is Tau and what does it do?

Answer 2

A microtubule associated protein (MAP) which causes them to become tightly packed bundles

Question 3

What is Kinesin-13 and what does it do?

Answer 3

A microtubule associated protein (MAP) which promotes catastrophe

Question 4

What are the two types of microtubule motor proteins and which end are they directed towards?

Answer 4

Kinesin - positive directed

Dynein - negative directed

Question 5

What does Thymosin B4 do?

Answer 5

Sequesters ATP-actin to prevent spontaneous microfilament formation

Question 6

What does profillin do?

Answer 6

Bind to ADP-actin causing ADP to dissociate and ATP to bind. ATP-actin can then join the microfilament

Question 7

What does cofillin do?

Answer 7

Binds to the negative end of the microfilament causing fragmentation leading to faster depolymerisation

Question 8

What does CapZ do?

Answer 8

Binds to the positive end of microfilaments, preventing growth. It is inhibited by PIP2

Question 9

What do he toxins cytochalasin D and Latruncilin do ?

Answer 9

Inhibit actin filament polymerisation

Question 10

What do formins do?

Answer 10

When activated by binding to Rho-GTP it catalyses actin nucleation by binding G-actin on it’s FH1 domain then passing these onto the FH2 domain where actin grows.

Question 11

What do ARp2 and Arp3 do?

Answer 11

Used as a template to create branches on actin filaments, This requires a regulatory protein such as WASp

Question 12

What are the bundling proteins

Answer 12

Fimbrin and alpha actinin

Question 13

What pinches off a clathrin coated vesicle?

Answer 13

The GTPase Dynamin

Question 14

What are the cyclins-cdk complexes in order from G1?

Answer 14

Cdk 4 Cyclin D
Cdk6 Cyclin D
Cdk 2 Cyclin E
Cdk 2 Cyclin A
Cdk 1 Cyclin E
Cdk 1 Cyclin B

Question 15

How do cyclins alter Cdk structure?

Answer 15

Cause PSTAIRE to rotate so that glutamate is close to the active site, so a saltbridge can form with lysine 33
The alphaL12 helix uncoils pulling the T-loop away from the active site

Question 16

How are cdks regulated by phosphorylation?

Answer 16

Wee1 inhibits cdk by adding 2 phosphate groups on thr-14 and tyr-15. Simultaneously CAK activates cdk by adding a phosphate on Thr-161, locking the T-loop in the open conformation. In order for the complex to be fully active cdc 25 must remove the inhibitory phosphates placed of thr-14 and thr-15 by wee1.

Question 17

How is the G1/S transition regulated?

Answer 17

It is regulated by Cdk inhibitor proteins (CKIs):
p16 - Cdk 4 and Cdk 6 (stop cyclin binding competitively)
p21 and p 27 - Cdk 2 (induce conformational change in the Cdk-cyclin complex to prevent cyclin activating cdk)

Question 18

How are cyclins destroyed?

Answer 18

E1 - Activates Ubiquitin
E2 - Conjugates Ubiquitin
E3 - Recognises D-box and transfers Ub from E2 to protein.
When a poly-Ub chain is on the protein it is detected by the lid structure of the proteasome and degraded.

Question 19

What are the 4 major cell cycle checkpoints?

Answer 19

Passage through the restriction point
DNA damage checkpoints
DNA replication stress checkpoints
Mitotic spindle checkpoints