M&R - G protein coupled receptors Flashcards
What do agonists at GPCRs do?
Bind to receptor and activate it
E.g B2 agonists - anti asthma
What is transduction?
A series of intracellular proteins that occur in series and bring about a cellular response
What do antagonists at GPCRs do?
Bind to receptors and do not activate it (block agonists)
E.g B - Antagonists treat hypertension
What are 3 genetic changes that can occur to GPCRs?
Retinitis pigmentosa- loss of function mutation to rhodopsin
Nephrogenic diabetes insipidus- caused by loss of function to vasopressin receptors
Familial male precocious puberty - caused by a gain of function mutation to LH receptor
What is the variety of stimuli that GPCRs respond to?
E.g ions (H+, Ca2+)
Neurotransmitters
Peptide and non peptide hormones
Large glycoproteins
How many CPCRs are in the human genome
865
What is the structure of G protein coupled receptors?
Single peptide with 7 transmembrane spanning domains
An Extracellular N terminal and an intracellular C terminal
Where are the 2 regions for ligand binding?
Between 2 or 3 of the transmembrane domains or in the N terminal region
Once the ligand is bounded to a G protein receptor what happens?
Induces a conformational change that is enough to activate a G protein
What are the 3 subunits that make up a G protein?
Aloha, beta, gamma
How is the G Protein activated?
The exchange of GDP for GTP on the alpha subunit
Once activated what happens to the subunits?
The alpha and beta-gamma complex dissociates the. Each interacts with effector proteins
How is the G protein signal terminated?
GTPase activity hydrolyses GTP back to GDP
The a - GDP and beta-gamma subunits then reform to the inactive heterotrimeric complex
What are the 4 types of G protein alpha subunit that acts on effectors?
Gs, Gi, Gq, Gt
What happens when adrenaline or NA acts on B adrenoceptors?
Gs alpha is activated and stimulates adenylyl cyclase activity
