Voltage gated sodium channel, alpha-1 subunit (IPR008051)
Short name: Na_channel_a1su
Overlapping homologous superfamilies
- Voltage gated sodium channel, alpha subunit (IPR001696)
- Voltage gated sodium channel, alpha-1 subunit (IPR008051)
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.
The SCN1A gene encodes the NaB1 channel and is particularly expressed in the brain, but is also found in a variety of other tissues, ranging from the retina to the olfactory bulb. Epilepsy, a disorder of neuronal hyperexcitability, has been associated with altered kinetics of SCN1A, as well as delayed inactivation of SCN2A [PMID: 11756608].
- PR01664 (NACHANNEL1)