Lecture 18 - enzyme coupled receptors Flashcards
how does phosp acc cause a change in protein activity
adds -ve charge
how could phosph cascade occur
many proteins that are controlled by phosph are kinases themselves
so when they get phsoph, they phosph the next thing
an example of protien kinase cascade
MAPK kinase cascade
what does ligan binding to RTK induce
dimerisation of inactive RTK monomers
what does the intracellular domain act as in RTK
catalytic site
when dimerised = act as kinases
what residue is transphosphorylated when RTK activated
tyrosine
when RTK is transphosphorylating, what can it now act as
a signalling complex
so other signalling proteins bind to this complex at the ‘docking sites’
what inactivates RTKs
protein tyrosi phosphatase
what does inactivation of RTK cause
receptor endocytosis
gets degraded in lysosome
what is RAS
a monomeric G protein that is downstream of RTK at plasma memb
(has same switch mechanism)
what allows exchange of GDP for GTP in RAS when it recieves a signal
RAS-GEF
for example SOS
what hydorlyses the GTP in an activated RAS
RAS-GAP
(the GAP will just enhance RASs GTPase activity
since RTKs allow RAS to be activated, what specific docking site on RTK allows this to happen
Y-P docking site
what binds to the Y-P docking site on RTK and how
GRB2 (an adaptor protein)
via its SH2 domain
binds to phospho tyrosine residue (hence Y-P)
what does the SH3 domain on GRB2 bind
SOS (the GEF) which then activates RAF
via the proline rich sequences
what does RAS go on to activate
MAP kinase kinase kinase
:/
how does MAP kkk omg get down to just MAP k
via ATP
what can activated MAPk do after phosph proteins
- alter cell metabolism
- alter response to stimuli
- can phosph cytoskeleton proteins = alter cell shape
- alter gene regulation
what is PI3K
a hetereodimeric lipid kinase
what does PI3K do
phosphorylates inositil lipids (e.g. PIP2 into PIP3)
2 examples of transduction pathway cross talk
- 2 diff ligands bind to 2 diff receptors,
the 2 repsonses prodcued phosph 2 diff sites on same protein - 2 diff ligands bind to 2 diff receptors,
they phosph 2 diff protein
these 2 dimerise
produce signal
