Figure 1.

The amino acid sequence of S4 in each motif of the wild-type channel and schematic representation of the wild-type and mutant Ca²⁺ channel α_1C subunits. (A) Amino acid sequence of the human heart L-type Ca²⁺ channel α₁ subunit S4. Conserved proline residues and equivalent positions are enclosed in a vertical box. Positively charged residues are underlined. (B) Diagrams describing the wild-type and mutant channels. Cylinders indicate transmembrane segments. S4s containing a proline are depicted as kinked cylinders.