There are four subfractions in the venom known to be active against the Spodoptera litura larvae: δ-palutoxin IT1, δ-palutxoin IT2, δ-palutoxin IT3, and δ-palutoxin IT4. These toxins are 36-37 amino acids long and show high homology. The concentrations of the different subtypes in the venom, molecular masses, and acidity level of the subtypes are listed below. Toxin subtype Concentration in venom (nmole/10µl) Molecular mass (kDa) Acidity level δ-Palutoxin IT1 1.0 4.03 Neutral δ-Palutoxin IT2 2.6 4.12 Slightly basic δ-Palutoxin IT3 1.3 3.93 Acidic δ-Palutoxin IT4 1.9 4.05 Slightly basic δ-Palutoxins are very compact proteins due to their four disulfide bridges. These bindings result in a disulfide pseudo-knot, characteristic for a class of toxins that contain the ‘inhibitor cystine knot motif’ (ICK). This motif is responsible for their high in vivo stability. Members of the ICK family are characterized by a triple-stranded, antiparallel β-sheet structure, stabilized by disulfide bridges. Within this fold-class, the biological activities of the toxins are very diverse. The disulfide bonding pattern found in δ-Palutoxins is very similar to the pattern seen in µ-Agatoxins. This indicates strong homologies with the µ-Agatoxins from Agelenopsis aperta.
Delta-Palutoxin
Maitotoxin
Psalmotoxin
Chlorotoxin
Kaliotoxin
Jingzhaotoxin
BeKm-1 toxin
Diamphotoxin