Figure 2. Sequence alignment of HCa with related toxins active on the RyR.

(A) Sequence alignment of HCa with four analogous toxins, MCa, IpTx A, opicalcine 1 and opicalcine 2. MCa and IpTx A are two peptides known to be active on the RyR. Opicalcine 1 and 2 have not been tested for pharmacological activity. All five toxins have the same number of positively charged amino acid residues (the N-terminal glycine residue, six or seven lysine residues and four or five arginine residues). (B) A sequence alignment of HCa with peptide A of the II–III loop of Ca_vα_1.1 subunit from the DHPR is also provided. The strongest homology stretches from Lys¹⁹ to Thr²⁶ of HCa.