Module 7.1 - Voltage-gated Na and K channels Flashcards
What family of ion channels are the NaV and KV channels part of?
P-loop family
What are p-loop channels named after?
Extracellular pore (P)-loops that project into the center of the folded protein.
What are the P-loop regions responsible for?
Ion selectivity
How many P-loops do P-loop channels need to be functional?
4
Outline the domains and their corresponding genes of the NaV channels.
Consist of four repeat domain (I to IV) encoded by single gene.
Outline the domains and their corresponding genes of the KV channels.
Consist of four domains encoded by a single-domain gene (i.e., four separate proteins must come together to form a complete channel)
How many transmembrane alpha helices are in each domain/subunit of the voltage-gated Na and K channels?
6 (S1-S6)
Which helices make up the lining of the ion channel pore? What do they possess?
S5 and S6
Possess the extracellular P-loops
Which helices make up the voltage sensors of the channels?
S1-S4
How are the S4 helices kept in the plane of the membrane at RMP?
S4 helices have positive AAs that are counterbalanced by negative AAs in S2 and S3 helices
At RMP, inner -ve charges and outer +ve charges keep S4 helices within plane
What happens to the S4 helices when the membrane is depolarized?
Protrude outwards
What does S4 helix protrusion cause? What is this called?
Conformational change in the channel which opens the pore.
Called channel activation
What causes the onset of the inward early current in the squid axon?
Activation of numerous NaV channels
Describe channel inactivation.
NaV channels have a plug in the cytoplasmic linker between domains III and IV that quickly plugs the pore.
What causes decay of the inward early current in the squid axon?
Inactivation of numerous NaV channels
