Ser/Thr Protein-Kinases and Phosphatases Flashcards
Kinases phosphorylate which AA’s?
Serine, threonine, tyrosine.
they have OH groups.
Kinase mechanism?
Nucleophilic attack catalyzed by kinase (does this by ideally positioning the rx. partners) of an OH group on the gamma phosphate of ATP
P is bulky and neg so it changes the enviro
Kinase structure?
Large and small lobe. Substrate often interacts with large lobe.
ATP binds cleft b/w lobes.
Glycine loop
Closed conformation of glycine loop in small loop forces gamma phosphate of ATP into correct position for phosphoyrlation
fast reaction
Open conformation: allows ADP to be exchanged for ATP
slow.
Need alternation!
Where can you inhibit kinases?
Active conformation is very conserved. So better to go at inactive conformation (distort ATP binding pocket… glycine rich loop, C-helix, activation loop)
Can block with pseudo-substrate
Upstream kinases activating more kinases
Example of this is MAPK pathway, stands for mitogen activated but mitogen might be way upstream
Cyclosporin and Rapamycin
Calcineurin and mTOR inhibs.. immunosuppressants
CamKII and Calcineurin
mediate long term depression, synaptic strength. Ca as a node.
How many kinases vs. phosphatases
way more kinases! so thought is that phosphatases are less specific/regulated
ATP general structure
purine base, ribose sugar, 3 p’s (alpha, beta, gamma), high energy phosphoanyhydride bonds
PKA
Activation loop needs to be phosphorylated into correct position (needed in some kinases not all)
GLycine rich loop clamps down on ATP to positition gamma phosphate
Small lobe: ATP binds, beta sheets, helix C (imp for ATP binding pocket)
Action happens in cleft!
large lobe: substrate binds
Catalytic sites are released and get P’ed to be active. tetramer.
CDK2
need cyclin, Phosphorylation of activation loop, removal of a P
