Voltage gated sodium channel, alpha subunit (IPR001696)

Short name: Na_channel_asu

Overlapping homologous superfamilies


Family relationships


Voltage-dependent sodium channels are transmembrane (TM) proteins responsible for the depolarising phase of the action potential in most electrically excitable cells [PMID: 1317577]. They may exist in 3 states [PMID: 1323284]: the resting state, where the channel is closed; the activated state, where the channel is open; and the inactivated state, where the channel is closed and refractory to opening. Several different structurally and functionally distinct isoforms are found in mammals, coded for by a multigene family, these being responsible for the different types of sodium ion currents found in excitable tissues.

The structure of sodium channels is based on 4 internal repeats of a 6-helix bundle [PMID: 6209577] (in which 5 of the membrane-spanning segments are hydrophobic and the other is positively charged), forming a 24-helical bundle. The charged segments are believed to be localised within clusters formed by their 5 hydrophobic neighbours: it is postulated that the charged domain may be the voltage sensor region, possibly moving outward on depolarisation, causing a conformational change. This model [PMID: 6209577] contrasts with another [PMID: 1323284], in which the TM segments are juxtaposed octagonally. The basic structural motif (the 6-helix bundle) is also found in potassium and calcium channel alpha subunits.

Cation channels are transport proteins responsible for the movement of cations through the membrane. These proteins contain 6 transmembrane helices in which the last two helices flank a loop which determines ion selectivity. In some sub-families (e.g. Na channels) the domain is repeated four times, whereas in others (e.g. K channels) the protein forms as a tetramer in the membrane.

This entry represents alpha subunits of the voltage-gated Na+ channel superfamily.

GO terms

Biological Process

GO:0006814 sodium ion transport

Molecular Function

GO:0005248 voltage-gated sodium channel activity

Cellular Component

GO:0001518 voltage-gated sodium channel complex

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.