Sodium channels Flashcards
Types of channels for sodium
There are voltage gated ion channels and ligand gated ion channels
Experiment to show sodium ion flow
Patch clamp experiments shows these results
When you depolarise sodium current will flow through sodium channel
After a while on 1.1 it declines back to its basal level due to inactive period
How many time does membrane cross
24 times
homologous domain
Every 6 segments form a homologous domain
Bacterial sodium
Bacterial sodium voltage gated channels have a different structure to normal sodium channels
S1-S4 is a detecting agent
The pore domain is formed by S5-S6
conserved arginine residue
S4 has 4 Highly conserved arginine residue which is positively charged
arginine residue appears in every 3 amino acids which forms a whole turn of alpha helix
Sliding helix model
When depolarised Intracellular potential becomes more positive so s4 pushes positive charge to move towards the extracellular side for sensing
Layers of the ion channel
The first outer part of the pore is the extracellular funnel
After there is a selectivity filter
Then there is a central cavity
S6
activation gate formed by S6 which can open and close the gate
S6 can also block sodium ions
Depolarisation in ion channels
There is a linker region which connects the VSD to the PD
When depolarisation of membrane voltage happens in S4 the outwards rotation will pull outwards
This can then cause S6 to cause bending causing opening of channel pore when s6 is straight the gate is closed
inactive gate
The inactive gate is formed by the intracellular loop between domain 3 and 4 composed of specific amino acid
If you delete the inactive gate region the current constantly stays at the peak current as there is no inactive state
Modulation of sodium channels
B subunits bind to alpha subunits in different ways and change the function of the channel by promoting or accelerating
Pharmacology use
Can be used to block brain channels and treat epilepsy
All drugs bind to S6
