Lecture 10: Molecular Structures

What is the general composition of voltage gated ion channels?

* made up of subunits (trace your finger along an amino acid chain without picking it up)
* membrane-spanning protein chains
* Usually, the alpha subunit is the pore or hole which the ion passes through
* beta and other subunits provide stabilization and other functions

What do amino acid chains do?

They fold up onto themselves to form a functional protein

Tertiary structure =

one subunit

6 transmembrane family

voltage gated sodium and potassium channels that largely take part in the action potential

What is needed to build a functional potassium voltage gated ion channel?

4 alpha subunits

What does transmembrane mean?

The acid strands have to travel from the outside to the inside of the cell

What is a difference between a voltage gated sodium channel and a voltage gated potassium channel?

sodium channel as 1 subunit with 4 pseudo-subunit regions whereas potassium just has 4 subunits

What is needed for a functional sodium voltage gated ion channel?

ONE alpha subunit made up of 4 repeating structures that make up the pore

Why are some subunits of the alpha region voltage sensitive?

allowing changes in conformation (shape) with voltage changes

What are the two opportunities for filtering?

1. When they have the water shell around them
2. When the water shell has been stripped

Does potassium or sodium attract more water molecules? Why is this important?

Sodium attracts more water molecules so it is bigger. This is important because it allows the channels to filter through the ions. The potassium ion channels have smaller openings that only potassium and its water ions can fit through

What is an ion channel made of?

An amino acid → protein

Is sodium or potassium bigger without the water shell?

Potassium is bigger without the water shell

What are charged voltage sensors?

positively charged proteins that move with changes in voltage, changing the conformation (shape) of the protein

What do charged voltage sensors do and where are the located?

These sensors pull the protein open at certain voltages. Towards the inside of the channel

What are some similarities and differences between voltage gated sodium channels and voltage gated potassium channels?

1. sodium channel has inactivation gate and potassium channel does not
2. sodium channel only has one alpha subunit whereas potassium has 4
3. Both are a part of the 6 transmembrane family
4. Both have voltage sensors