Inhibits high (L-type) voltage-activated calcium channels (Cav) in a calcium-dependent manner. Expressed by the venom duct. The cysteine framework is C-C. In contrast to the other contryphans, glacontryphan-M is a single homogenous conformer exhibiting no cis to trans isomerization of the Cys-Pro peptidyl bond in aqueous solution. Belongs to the O2 superfamily. Contryphan family.