Ligand Gated Ion Channels Flashcards
What is an ion channel?
- A transmembrane protein that transports molecules from one side of the membrane to the other
- Regulates membrane potentials
- Controls Ca2+ flux into cytoplasm
What is a P loop?
Where the ion binds in the channel
What makes up an ion channel?
- 2 or more alpha helices
- 2-6 subunits surrounding the pore
How many genes code for membrane channels?
400
What is a simple ion K+ channel?
Channel with 2 transmembrane domains (trimeric)
Helicase forms the P loop.
Does K+ fit into the pore?
K+ has to lose a H2O molecule to fit in the pore.
What is the structure of a voltage gated ion channel?
Similar to simple ion channel, with additional helices (S1 and S4) which create the voltage sensing domain.
Large polypeptides in the cytoplasm for sensing.
Amino acids can plug the channel.
What is a TRP?
Voltage gate that senses chemical and physical stimuli.
Structure of a Cys loop receptor?
Pentameric, 5 subunits, 4 TM domains.
Intracellular loop betweenM3 and M4.
What happens when chronic exposure of nicotine occurs?
Receptor upregulation
What ionotrophic receptors of EC ligand gated ion channels are there?
Pentameric - 4 TMs, e.g. Nicotine receptors
Tetrameric - 3 TMs, e.g. Glutamate receptors
Trimeric - 2 TMs, e.g. ATP receptors
What happens when each of the ionotrophic receptor families disregulate?
Pentameric - epilepsy
Tetrameric - stroke, neuron death
Trimeric - hearing loss, pain, inflammation
What does a mutation in nACHR cause?
Autosomal dominant nocturnal frontal lobe epilepsy. Mutation in M2, unblocking of closed receptors.
What are glutamate receptors?
Tetrameric, 3 TMs. Receptors in brain, split into different groups due to RNA splicing and editing.
What are the groups of glutamate receptors?
AMPs - AMPA receptors, fast excitory response at synapses.
NMDA - learning and memory, slower response
Kainate - similar to AMPAs but less synapses.
