Inhibits high voltage-activated calcium channels (Cav). Expressed by the venom duct. The cysteine framework is C-C. in the brominated form (Ama1054). Three forms of this peptide have been described. Am918 is 7 residues long and is hydroxylated and amidated; Am975 is 8 residues long and is also hydroxylated and amidated, while Ama1054 is only different from Am975 by an additional Trp bromination. An amidated peptide of 8 residues with identical sequence but without hydrolation is described in Conus buxeus loroisii venom (AC P0C250). Exists in two forms, due to cis-trans isomerization (possibly at 56-Cys-hydroxyPro-57). The cis conformation is the major form. Belongs to the O2 superfamily. Contryphan family.