Activates high voltage-activated calcium channels (Cav). This activity is in contrast to other contryphans that inhibit high voltage-gated calcium channels. Expressed by the venom duct. The cysteine framework is C-C. Monoisotopic mass. Exists in two forms, due to cis-trans isomerization at 56-Cys-Pro-57. Belongs to the O2 superfamily. Contryphan family.