Ligand-Gated Ion Channels Flashcards
Is the resting state of ion channels open or closed?
Closed
Why is the resting state of ion channels closed?
In order to allow for the build up of charge
What is the function of nicotinic acetylcholine receptors?
Convert binding of acetylcholine into membrane electrical signal
What diseases is disfunction of nicotinic acetylcholine receptors linked to?
- Diabetes
- Depression
- Alzheimer’s
- Epilepsy
What is the natural ligand for nicotinic acetylcholine receptors?
Acetylcholine
Is acetylcholine an agonist or antagonist for nicotinic acetylcholine receptors?
Agonist
Why does acetylcholine bind to nicotinic acetylcholine receptors with a relatively low affinity?
So it can be released from the receptor
Is nicotine an antagonist or agonist for nicotinic acetylcholine receptors?
Agonist
What is the general structure of nicotinic acetylcholine receptors?
Homo or heteropentamer with 2-5 binding sites
What kind of subunits are skeletal muscle nicotinic acetylcholine receptors made up of?
- 2α
- 1β
- 1γ
- 1δ
Where is the ligand binding site on skeletal muscle nicotinic acetylcholine receptors?
- On the outside of the membrane
- Shared between γ and α subunits
What happens when the ligand binds to nicotinic acetylcholine receptors?
- Opens central channel
- Has an allosteric effect
What is the allosteric effect of a ligand binding to a nicotinic acetylcholine receptor?
- Flexible loop wraps around ligand
- Buried ligand makes extensive hydrophobic contacts
- Side chains rearrange in the binding site to accomodate ligand
- These local changes result in large rotational movements to open the channel
How does curare act as a poison?
Directly competes with acetylcholine and acts as an antagonist
How does nicotine bind strongly to nicotinic acetylcholine receptors?
- Makes hydrophobic interactions
- Makes H bonds with protein backbone
- Makes 2 hydrogen bonds (one with water, one with W143)
