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BIOB11H3 (300)
Lecture 11

BIOB11H3 Lecture Notes - Lecture 11: Adenylyl Cyclase, G Protein-Coupled Receptor Kinase, Arrestin


Department
Biological Sciences
Course Code
BIOB11H3
Professor
Daman Bawa
Lecture
11

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GPCR Mechanism of Action
1) Ligand binds to the extracellular side which results in a conformational change that
increases the affinity for G proteins in the cytosol. The receptor then binds the G protein
intracellularly
2) GDP is exchanged for GTP which activated the G protein
3) Binding of GTP lowers the affinity of G-alpha subunit for G-beta and G-gamma subunits.
Dissociation occurs and the G-alpha subunit then binds to the effector molecule
4) Effector is activated which generates a second messenger (adenylate cyclase generates
cAMP)
5) GTP is hydrolyzed (GTP GDP + Pi) which inactivates the G-alpha subunit
6) Inactivated G-alpha subunit loses affinity for the effector and regains affinity for G-beta
and G-gamma subunits. The effector is inactivated and second messenger is not
generated
7) G protein-coupled receptor kinases (GRKs) recognize and phosphorylate activated
GPCRs
8) Phosphorylation recruits arrestin protein which competes for binding with the G
protein. This results in no further binding and activation of the G protein. This is called
receptor desensitization
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