摘要：Cytotoxic proteins have a wide applicability in human therapies, especially in those conditions that require efficient and selective cell killing, such as cancer. Chlorotoxin (CTX) is a small (4 kDa) basic peptide from the venom of the yellow scorpion Leiurus quinquestriatus , which blocks small-conductance chloride channels thus paralyzing the scorpion prey. Being not extremely potent as a cytotoxin (for instance when compared with ribosome-inactivating proteins), it has gained interest as a targeting agent.