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.