Receptor mechanisms II Flashcards
What is the overall structure of the G protein coupled receptor
7 transmembrane regions, an agonist site and a G binding site
What is the resting state of the G protein complex
The alpha subunit is bound to
- GDP
- The gamma and beta subunit dimer
- The G-protein coupled receptor
What do the the gamma and beta subunits do
They inhibit the alpha subunit when its bound to GDP
They also act as membrane anchors
What happens when an agonist binds to the G-protein coupled receptor
the guanine nucleotide exchange factor domain allosterically activates the activation of the alpha sub unit by exchanging GDP for GTP
What happens to the activated alpha sub unit
It dissociates from the receptor and the beta-gamma subunits
It goes on to activate an specific enzyme
How is the alpha sub unit deactivated
Overtime the GTP is hydrolysed back to GDP
The alpha subunit rebinds to the beta-gamma subunits and also the receptor
What does alpha Gs do
Stimulates adenylate cyclase which makes cAMP from ATP
What does cAMP do
Activates protein kinase A which will phosphorylate many molecules
What is cAMP broken down by
phosphodiesterase
What does alpha Gis do
Inhibits adenylate cyclase so there is less ATP being made into cAMP
What does alpha Gq/11 do
Activates phospholipase c
What does phospholipase C do
Cleaves PIP2 which makes DAG which stays in the lipid phase and IP3 which is water soluble and goes through the cytoplasm
What does IP3 do
Binds to its receptor that tends to be located on the intracellular calcium stores, causing the release of calcium that is used in contractile proteins
What does DAG do
Activates various ion channels and activates protein kinase C
What does adrenaline do
Acts as a signal amplification molecule, can make around 10,000 cAMP molecules
