7 - Targeted Therapies – Melanoma Flashcards
What are the most common point mutations in BRAF
AA-464-9 and 600
Where do the most common mutations occur on RAF proteins (2)
Critical catalytic sites:
Phosphate binding loop
Activation loop
What is an important signalling pathway for melanoma
MAPK
What is the starting signal for the MAPK signalling pathway
Tyrosine kinase receptor
What does BRAF consist of
2 dimerised protomers
How many states does BRAF exist in
Two
Inactive (monomer)
Active (dimer)
When is the BRAF structure stabilised for catalytic activation
aC helix moving into ‘in’ conformation
What does BRAF WT mutation do
Valine interacts with phenyl ring of F467 on P loop, keeping A loop in an inactive confirmation
What does BRAF V600E mutation do
Changes mutation sized valine to larger charged residue (Glu, Asp, Lys, Arg) which destabilises interactions with F467 and flips A loop into active formation
Glu600 can form salt bridge with Lys 507 to keep A loop in active state
What does vemurafenib do
Inhibits ATP binding site when in the active confirmation BRAF kinase
How much inhibition does Vemurafenib require for a clinical response
> 80% target inhibtion
What is the structure of the BRAF protomer
Typical kinase structure
2 lobes linked by a hinge region attached by an ATP binding cleft
How many protomers does vemurafinib bind to
One protomer
How does vemurafenib work
Conformational change in aC helix and stabilises the protein in active confirmation
What tail is an ideal fit in the RAF interior pocket
Propyl
