CBG32

Question 1

What is nAChR?

Answer 1

Nicotonic Ach receptor

major receptor at neuromuscular junction - first ligand gated receptor protein to be purified.

Question 2

Why was nAChR the first ligand gated receptor to be purified?

Answer 2

1. high concentrations found in great numbers in electroplax organ of eimobrach (electric eel) and teleost
   - 1kg of electrical organ contains over 100mg of
   receptor protein.
2. sensitivity of nAChR’s to alpha-BTX - a component of cobra venom useful in study to tag AChRs

Question 3

What is the structure of the nictotine acetylcholine receptor?

Answer 3

pentametric
- 5 proteins subunits associated to form a transmembrane channel. 2xalpha 1xdelta 1xlambda 1xbeta
- alpha subunits contain sites that bind ACh
- negatively charge internal portion bears the selectivity filter for Na+ and K+
Each subunit is 55kDa
- 275KDa in total

Question 4

What happens when ACh binds to alpha subunit

Answer 4

causes a conformational change 
pore opens 
Na+ flow in/K+ out down electrochemical gradient
excitatory receptor
membrane deploarisation

Question 5

What are the 3 functional states of nAChR?

Answer 5

1. resting - closed - no ACh bound.
2. Activated - open - 2ACh bound - can flicker between open and closed state with ACh bound
3. Desensitised - ACh still bound but closed

Question 6

what is gaba?

Answer 6

the chief inhibitory neurotransmitter in the mammalian central nervous system. It plays the principal role in reducing neuronal excitability throughout the nervous system.

Question 7

What is the structure of muscarinic acetylcholine receptor mAChR?

Answer 7

460AA
70kDA
7TM receptor
interacts with 6 proteins