Conantokins inhibit N-methyl-D-aspartate (NMDA) receptors. This toxin has the highest potency for the NR2B/GRIN2B subunit. It induces sleep in 10-day-old mice when injected intracranially, and hyperactivity in 24-day-old mice. Expressed by the venom duct. The mature peptide does not contain cysteine residue. Adopts an alpha-helical conformation in presence and in absence of divalent cations. Belongs to the conotoxin B superfamily.