Chlorotoxin is a 36-amino acid peptide found in the venom of the deathstalker scorpion (Leiurus quinquestriatus) which blocks small-conductance chloride channels. The fact that chlorotoxin binds preferentially to glioma cells has allowed the development of new methods, that still are under investigation, for the treatment and diagnosis of several types of cancer. Chlorotoxin is the first reported high-affinity peptide ligand for Cl- channels and it blocks small conductance chloride channels. Each chloride channel can be closed by only one ligand molecule. Using a recombinant chlorotoxin it was demonstrated that chlorotoxin specifically and selectively interacts with MMP-2 isoforms which are specifically upregulated in gliomas and related cancers, but are not normally expressed in brain. Chlorotoxin immobilizes the envenomated prey.
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