Figure 2: A novel missense mutation in exon 19 of SCN4A was identified in the patients with paramyotoniacongenita. A substitution of thymine with adenine at position 3470 changes the codon for isoleucine at position 1157 into asparagine. B: Amino acid sequences of Nav1.4 channels from various species are aligned. Isoleucine residue at position 1157 (black arrowhead), which is mutated in the patients, is conserved across the various species. C: Schematic representation of the alpha subunit of Nav1.4 channel showing the six trans-membrane segments (S1-S6) of each of the four domains (D1-D4) and the location of the p.Ile1157Asn mutation (black dot). This mutation is located on the cytoplasmic link between S4 and S5 of D3.