Voltage gated sodium channel, alpha subunit (IPR001696)
Short name: Na_channel_asu
Overlapping homologous superfamilies
- Voltage gated sodium channel, alpha subunit (IPR001696)
- Voltage gated sodium channel type 4, subunit alpha B (IPR028817)
- Voltage gated sodium channel, alpha-1 subunit (IPR008051)
- Voltage gated sodium channel, alpha-10 subunit (IPR028809)
- Voltage gated sodium channel, alpha-11 subunit (IPR028821)
- Voltage gated sodium channel, alpha-4 subunit, mammalian (IPR008052)
- Voltage gated sodium channel, alpha-5 subunit (IPR008053)
- Voltage gated sodium channel, alpha-7 subunit (IPR028812)
- Voltage gated sodium channel, alpha-8 subunit (IPR008054)
- Voltage gated sodium channel, alpha-9 subunit (IPR028803)
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.
- PR00170 (NACHANNEL)