κ-Conotoxin RIIIJ (κ-M-RIIIJ), is a 25 amino-acid peptidyl toxin belonging to the Conotoxin M superfamily. This conopeptide inhibits the homotetrameric human KV1.2 channels (IC50 = 33 nM)3. κ-M-RIIIJ was found to exert cardioprotective effects, presumably due to the high affinity of this peptide for mammalian KV1.2 and KV1.2- containing heteromultimers