Voltage-gated ion channel

Each of the four homologous domains makes up one subunit of the ion channel. The S4 voltage-sensing segments (marked with + symbols) are shown as charged.
Identifiers
Symbol	VIC
Pfam clan	CL0030
TCDB	1.A.1
OPM superfamily	8
OPM protein	2a79

Voltage-gated ion channels are a class of transmembrane proteins that form ion channels that are activated by changes in the electrical membrane potential near the channel. The membrane potential alters the conformation of the channel proteins, regulating their opening and closing. Cell membranes are generally impermeable to ions, thus they must diffuse through the membrane through transmembrane protein channels. They have a crucial role in excitable cells such as neuronal and muscle tissues, allowing a rapid and co-ordinated depolarization in response to triggering voltage change. Found along the axon and at the synapse, voltage-gated ion channels directionally propagate electrical signals. Voltage-gated ion-channels are usually ion-specific, and channels specific to sodium (Na⁺), potassium (K⁺), calcium (Ca²⁺), and chloride (Cl⁻) ions have been identified.^[1] The opening and closing of the channels are triggered by changing ion concentration, and hence charge gradient, between the sides of the cell membrane.^[2]