 Phrixotoxin-1 and -2 are similar to heteropodatoxin, which also has a blocking activity on Kv4.2 channels .Phrixotoxin-1, -2 and -3 contain an Inhibitor Cystine Knot (ICK) motif, and thus belong to the ICK peptide family.Phrixotoxin-1 and -2 bind to A-type, transient, voltage-gated potassium channels, near the S3 and S4 segments, where they negatively affect transmembrane movement of the voltage sensing domain in response to depolarizing voltages.