G-protein coupled receptors

Question 1

Ionotropic definition

Answer 1

Receptors (ligand-gated ion channels) - direct exchange of ions through a pore in the ion channel

Question 2

Metabtropic Receptor definiton

Answer 2

Indirectly linked to ion channels through signal transduction mechanisms such as G proteins.

Question 3

What are the structural features of GPCRs

Answer 3

• 7 TMs linked by extracellular and intracellular loops
  -TM3 centrally located next to the binding pocket and is crucial for transduction of ligand binding
  -GPCR classes are distinguished by structural features of the extracellular domains

Question 4

What do G proteins do

Answer 4

They act as molecular switches inside cells to transmit signals from extracellular stimuli to downstream effectors

Question 5

What are G proteins regulated by

Answer 5

The ability to bind and hydrolyse GTP to GDP

Question 6

Basic mechanism of GPCRs

Answer 6

1. Alpha subunit binds to pocket
2. Alpha subunit in its resting state is bound to GTP. When bound to receptor, is displaced by GDP
3. It dissociates from the membrane and dissociates from the other two subunits so you end up with 3 active components
4. It moves through the membrane to react with its downstream effectors, eliciting a celllular response

Question 7

Mechanism of action for G proteins

Answer 7

1. Ligand binding causes a confirmational change in receptor that activates G protein
2. GDP is released and alpha subunits seperates and binds to GTP
3. Binds to target protein in membrane to elicit response within cell

Question 8

How is G protein signalling controlled

Answer 8

Time