Iota-conotoxins bind to voltage-gated sodium channels (Nav) and act as agonists by shifting the voltage-dependence of activation to more hyperpolarized levels (By similarity). Both natural (L-Thr form) and synthetic (D-Thr form) peptides cause paralysis and death following intracranial injection and grooming and hypersensitivity upon intraperitoneal injection into mice. The L-Thr form of the peptide is 7-fold more potent than the D-Thr form. Both natural peptide (L-Thr form) and synthetic peptide (D-Thr form) are active on nerve, and on muscle. Expressed by the venom duct. The cysteine framework is XI (C-C-CC-CC-C-C). Position 41 corresponds to a L-threonine, and not a D-threonine as firstly supposed. Belongs to the conotoxin I1 superfamily.