Sodium Channel Voltage Gated Type IV Beta (SCN4b)

The deduced 228-amino acid protein has a calculated molecular mass of about 22 kD. SCN4B has an N-terminal signal peptide, a large extracellular domain predicted to form an Ig-like fold, a single transmembrane alpha helix, and a short cytoplasmic C terminus. Two conserved cysteines likely form an intramolecular disulfide bond that stabilizes the large extracellular domain, and an unpaired cysteine likely forms a disulfide linkage with the alpha subunit. SCN4B shares 35% amino acid identity with SCN2B and 20 to 22% identity with SCN1B and SCN3B. SCN4B shares 80% amino acid identity with rat and mouse Scn4b. Quantitative RT-PCR analysis, in situ hybridization, and immunocytochemical analysis of rat tissues detected wide expression of Scn4b in neurons in the brain and spinal cord and in some sensory neurons.