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Flashcards in Stuff I need to learn Deck (19):

Within the centrosomes from what do microtubules nucleate?

The gamma tubulin ring


What is Tau and what does it do?

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


What is Kinesin-13 and what does it do?

A microtubule associated protein (MAP) which promotes catastrophe


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

Kinesin - positive directed
Dynein - negative directed


What does Thymosin B4 do?

Sequesters ATP-actin to prevent spontaneous microfilament formation


What does profillin do?

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


What does cofillin do?

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


What does CapZ do?

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


What do he toxins cytochalasin D and Latruncilin do ?

Inhibit actin filament polymerisation


What do formins do?

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.


What do ARp2 and Arp3 do?

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


What are the bundling proteins

Fimbrin and alpha actinin


What pinches off a clathrin coated vesicle?

The GTPase Dynamin


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

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


How do cyclins alter Cdk structure?

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


How are cdks regulated by phosphorylation?

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.


How is the G1/S transition regulated?

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)


How are cyclins destroyed?

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.


What are the 4 major cell cycle checkpoints?

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