SCN4A
Domain
The sequence contains 4 internal repeats, each with 5 hydrophobic segments (S1, S2, S3, S5, S6) and one positively charged segment (S4). Segments S4 are probably the voltage-sensors and are characterized by a series of positively charged amino acids at every third position.
Function
Pore-forming subunit of Nav1.4, a voltage-gated sodium (Nav) channel that directly mediates the depolarizing phase of action potentials in excitable membranes. Navs, also called VGSCs (voltage-gated sodium channels) or VDSCs (voltage-dependent sodium channels), operate by switching between closed and open conformations depending on the voltage difference across the membrane. In the open conformation they allow Na(+) ions to selectively pass through the pore, along their electrochemical gradient. The influx of Na+ ions provokes membrane depolarization, initiating the propagation of electrical signals throughout cells and tissues (PubMed:11834499). Highly expressed in skeletal muscles, Nav1.4 generates the action potential crucial for muscle contraction (PubMed:18317596, PubMed:21881211).
Sequence Similarities
Belongs to the sodium channel (TC 1.A.1.10) family. Nav1.4/SCN4A subfamily.
Tissue Specificity
Detected in quadriceps muscle (at protein level) (PubMed:18317596). Detected in hind-limb skeletal muscles, but not in heart or brain (PubMed:18317596). Detected at low levels in the myocardium. According to Pubme=26427606 detected also in brain.
Cellular localization
- Cell membrane
- Multi-pass membrane protein
Alternative names
Sodium channel protein type 4 subunit alpha, Sodium channel protein skeletal muscle subunit alpha, Sodium channel protein type IV subunit alpha, Voltage-gated sodium channel subunit alpha Nav1.4, Scn4a