M&R Flashcards
How many transmembrane domains does a GCPR have
7
How many subunits does a G protein have and what are they
3 (alpha, beta and gamma)
What happens to the GCPR molecule when a substrate binds to it.
Conformational change
Describe the steps during the activation process of G proteins
Ligand binds to GCPR which undergoes a conformational change
This change allows the alpha subunit of the G protein to exchange a GDP molecule for a GTP and the dissacociate away from the beta and gamme subunits
The alpha subunit (rarely can be gamma or beta subunits) can the interact with a target protein such as an ion channel or enzyme
GTP is then hydrolysed back into GDP and cycle restarts.
Describe how the target enzyme, Phospholipase C, works
Phospholipase C splits PIP2 into DAG and IP3
IP3 then causes the SER to release Ca2+ which activates another enzyme called PKC
DAG also directly activated PKC
PKC then phosophorylates various enzymes causing them to activate or inactivate
Describe how the target enzyme, Adenylyl cyclase, works
Adenylyl cyclase converts ATP to cAMP
cAMP then activated PKA which phosphorylates various proteins either activating or inactivating them
This leads to an increase in HR, dilation of skeletal muscles blood vessels and the conversion of glycogen to glucose.
This enzyme is stimulated by Gs and inhibited by Gi proteins
What mneumonic is used to remeber which G coupled protein is linked to which receptor
QISS QIQ
α1 Q
α2 I
β1 S
β2 S
M1 Q
M2 I
M3 Q
What recpetor responds to light in the eye?
Which G protein is it related to?
What is the effect of the G protein?
Rhodopsin Receptor which are linked to Gt proteins stimulating Cyclic GMP causing visual excitation
What changes do the following G proteins cause:
Gq?
Gi?
Gs?
Gq: Stimulate Phospholipase C
Gi: Inhibit Adenylyl Cyclase
Gs: Stimulate Adenylyl Cyclase
