Ras and MAP kinase Flashcards
1
Q
What are sevenless flies missing?
A
- no R7, a tyrosine kinase receptor
2
Q
What does not happen in sevenless flies?
A
- RTK receptor stimulated by FGF and stimulates production if R7 cell
3
Q
How was Ras shown in drive cell proliferation?
A
- Temperature sensitive sevenless flies were grown at a non-permissive temperature
- If mutant alleles of Ras were expressed by flies even at non-permissive temperature the flies could still develop R7 cell
4
Q
What kind of molecule is Ras?
A
- Small GTPase
5
Q
How is sos activated?
A
- RTK activated and phosphorylates itself
- Recruits Grb2 adaptor with SH2 domain to bind to phosphotyrosine residue
- Also contains SH3 domains which bind to polyproline sequences on sos
6
Q
How does sos activate ras?
A
- It is a Ras GEF
- Replaces GDP and Pi on Ras with GTP
- Ras adopts an active conformation and can interact with downstream molecules
7
Q
Which molecule activates Ras?
A
sos
8
Q
Where is Ras anchored?
A
At the cell membrane
9
Q
How does GTP binding cause Ras to be activated?
A
- GTP binding causes conformational change which exposes switch I and switch II regions
- These switch regions can interact with (and in many cases activate) downstream effector molecules
10
Q
How does Ras downregulate its own signal?
A
By hydrolysing GTP
11
Q
What geographical effect do Ras associated receptors have?
A
When activated brings proteins to the membrane and recruits cellular proteins into complex
12
Q
How is Ras regulated?
A
- inherent GTPase activity
- Ras GDI
13
Q
How does Ras GDI regulate Ras?
A
- GDI binds to the lipid anchor of Ras and sequesters it so it unable to embed in the plasma membrane
14
Q
What kind of molecule is Raf?
A
Ser/Thr kinase
15
Q
What is a MAP kinase kinase kinase?
A
Raf
