G protein coupled receptors Flashcards
1
Q
G-protien coupled receptor
A
- Most commonn receptor most have one or more GPCR
- Neurotransmitters and hormons have lots of GPCR
2
Q
Response of G protien
A
- When ligand binds to the receptor activating the G protien then the alpha and the GDP diacossiates from beta gamma
- Alpha and the GDP converts to GTP binds to the effector on the cell membrane causing a physological response
3
Q
Structure of G protien couple receptor
A
- 7 trans membrane domains
- Extracellular N terminus
- Intracelluar C terminus
- 3extracellular loop and 3 intracellular loop
- Similar structure to Adenaline intracellular binding
- FSH intracellular binding
4
Q
What are G protiens
A
- Guanine nucleotides bound protien
- Heterotrimic protiens
- Located intracellular lipd anchors help to mobllise the intracellular membrane
5
Q
G alpha
A
binds to guanosine diphosphate or guanosine triphosphate
6
Q
G beta gamma
A
- Dimer subunit
7
Q
G-protien cycle
A
- When resting Gabinds GDP and forms a complex with Gbg
- Upon ligand binding, GPCRs gets activated and catalyse exchange of GDP
for GTP on Ga - Ga-GTP and Gbgdissociate from each other and activate effector proteins
- The GTPase activity of Gaconverts bound GTP back to GDP
- Ga-GDP reassociates with Gbg, returns to inactive state
8
Q
G-protien effector
A
- Enzyme is usually effector
- Alpha subuit determine a specific response of either stimulatory or inhibitory
9
Q
Gs alpha
A
- Adenyal cyclase seconds messenger to cAMP with stimulatory efffects neurotransmitter release to smooth muscle for relaxation
- Activated by B1, B2 and B3 adenoreceptors - Adrenaline
10
Q
Gia apha
A
- Adenyl cyclase cAMP
- Inhibition of neurotransmitter release smooth muscle contraction
- alpha 2 adenoreceptors - adrenline
- M2 and M4 muscarinic receptor - acetylcholine
11
Q
Gq alpha
A
- Phospholipase C caises second messenger reaction to calcium
- Stimulates neurotransmitter release for smooth muscle contraction
- alpha 1 adenoreceptors - adenaline
- M1, M3 and M5 muscarinic receptor - acetylcholine
12
Q
Gs alpha
Second messenger model
A
- Ligand binds and causes the detachment to the apha subunit and GDP then acts on the adenyl cyclase effector
- Takes intracellular ATP and adenyl cyclase converts it to cAMP
- cAMP messenger to activate protien kinase A (can be phosphorylated) by binding to the regulatory subunit
- Dissociation of regulatory subunits from catalytic causes activation of target protien to cause physological response as protien is phosphorylated
13
Q
Example of second messenger model heart
A
- Smooth muscle myosin light chain kinase
- Calicum channel cardiac neural
- Transcription factor
14
Q
Regulation of cyclic AMP levels
A
- Phosphodiesterase breaks down cyclic AMP to 5-AMP
- 5-AMP then converted into ATP ready for the next cycle of cAMP
15
Q
Gia alpha subunit
Second messenger cAMP
A
- Ligand binds causing alpha subunit and GDP to detach and attach after converting to GTP to the effector
- Once bound it inhibits enzyme activity of adenyl cyclase causing to blocking of the conversion of ATP to cAMP therefore cannot activate protien kinase
