Membrane transporter/Ion channel - ALL Chemistry-Custom Chemical Solutions Supplier

Membrane transporter/Ion channel

What is Ion Channel?

Ion channels are protein molecules that span across the cell membrane allowing the passage of ions from one side of the membrane to the other. They have an aqueous pore, which becomes accessible to ions after a conformational change in the protein structure that causes the ion channel to open. Ion channels are selective meaning that they only allow certain ions to pass through them, and they play critical roles in controlling neuronal excitability^[1].

Fig.1 Ion channel

Basic Features

There are two distinctive features of ion channels that differentiate them from other types of ion transporter proteins^[2]:

(1) The rate of ion transport through the channel is very high (often 106 ions per second or greater).

(2) Ions pass through channels down their electrochemical gradient, which is a function of ion concentration and membrane potential, "downhill", without the input (or help) of metabolic energy (e.g. ATP, co-transport mechanisms, or active transport mechanisms).

Classification

There are many kinds of ion channels. Ion channels may be classified by the nature of their gating, the species of ions passing through those gates, the number of gates (pores) and localization of proteins.

Classified by gating, ion channels include voltage-gated channels, ligand-gated channels, light-gated channels, lipid-gated channels and other channels.

Classified by type of ions, ion channels include Cl- channels, K+ channels, Na+ channels, Ca2+ channels, proton channels and other channels.

Fig.2 Different ion channel types

Diseases

There are several disorders which disrupt normal functioning of ion channels and have disastrous consequences for the organism. Genetic and autoimmune disorders of ion channels and their modifiers are known as channelopathies.

It can be divided into congenital ion channel diseases and acquired ion channel diseases, in which the latter can be caused by abnormal gene expression and the presence of antibodies and other substances. According to the change of ion channel function, it can be divided into Gain-of-function and Loss-of-function ion channelopathy. Depending on the source of the disease, there are different targeted treatments.

Reference

[1] B.S Barker, G.T. Young, C.H. Soubrane, et al (2017). Conn's Translational Neuroscience, p11-43.

[2] Hille B (2001) [1984]. Ion Channels of Excitable Membranes (3rd ed.). Sunderland, Mass: Sinauer Associates, Inc. p.5.

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