Spider toxins of the CSTX family are ion channel toxins containing an inhibitor cystine knot (ICK) structural motif or Knottin scaffold. The four disulfide bonds present in the CSTX spider toxin family are arranged in the following pattern: 1-4, 2-5, 3-8 and 6-7. CSTX-1 is the most important component of C. salei venom in terms of relative abundance and toxicity and therefore is likely to contribute significantly to the overall toxicity of the whole venom. CSTX-1 blocked rat neuronal L-type, but no other types of HVA Cav channels [3]. Interestingly, the omega-toxins from Phoneutria nigriventer venom (another South American species also belonging to the Ctenidae family) are included as they carry the same disulfide bond arrangement. suggestive that CSTX-1 may interact with Cav channels. Calcium ion voltage channel heteromultimer containing an L-type pore-forming alpha1-subunit is the most probable candidate for the molecular target of CSTX-1 and these toxins [3].

1: A lysine rich C-terminal tail is directly involved in the toxicity of CSTX-1, a neurotoxic peptide from the venom of the spider Cupiennius salei. Kuhn-Nentwig L, Schaller J, Kampfer U, Imboden H, Malli H, Nentwig W; Arch Insect Biochem Physiol. 2000;44:101-111. PMID:10897091

2: CSTX-9, a toxic peptide from the spider Cupiennius salei: amino acid sequence, disulphide bridge pattern and comparison with other spider toxins containing the cystine knot structure. Schalle J, Kampfer U, Schurch S, Kuhn-Nentwig L, Haeberli S, Nentwig W; Cell Mol Life Sci. 2001;58:1538-1545. PMID:11693532

3: CSTX-1, a toxin from the venom of the hunting spider Cupiennius salei, is a selective blocker of L-type calcium channels in mammalian neurons. Kubista H, Mafra RA, Chong Y, Nicholson GM, Beirao PS, Cruz JS, Boehm S, Nentwig W, Kuhn-Nentwig L; Neuropharmacology. 2007;52:1650-1662. PMID:17517422