Conantokins inhibit N-methyl-D-aspartate (NMDA) receptors. This toxin is selective for the NR2B/GRIN2B subunit. Induces sleep-like symptoms in young mice and hyperactivity in older mice. Divalent cations stabilize the toxin the in alpha-helix conformation. Expressed by the venom duct. Failed in phase II clinical trial. Was tested under the name CGX-1007 by Cognetix Inc. to treat convulsion and epilepsy. The mutant Gln-89 consists of the addition of a proline residue which is hydroxylated (4-hydroxyproline). The mature peptide does not contain cysteine residue. Belongs to the conotoxin B superfamily.