Pi4 is a38-residue toxincross-linkedby fourdisulfidebridges that has been isolated from the venom of the Chactidae scorpion Pandinus imperator. Together with maurotoxin, Pi1, Pi7 andHsTx1, Pi4belongs to theaKTX6 subfamilyof short four-disulfide-bridged scorpion toxins acting on K + channels. Due to its very low abundance in venom, Pi4 was chemically synthesized in order to better characterize its pharmacology and structural properties. An enzyme-based cleavage of synthetic Pi4 (sPi4) indicated half-cystine pair-ings betweenCys6–Cys27, Cys12–32, Cys16–34 andCys22– 37, which denotes a conventional pattern of scorpion toxin reticulation (Pi1/HsTx1 type)
