Conserved Site

Omega-agatoxin type II/III, conserved site (IPR005853)

Short name: Omega-agatoxin_II/III_CS


Spider venoms often contain many active peptides, such as neurotoxins, lectins, and enzyme inhibitors, which are important for both hunting and defence. Starting from a common ancestor these peptides have evolved into a diverse array of toxins with different structures and functions. These toxins contain contain a relatively high number of cysteine residues, generally ranging from 6 to 14 [PMID: 15225557]. Several peptide toxins, collectively referred to as omega-toxins, block the different types of voltage-gated Ca2+ channels with differential selectivity.

Omega-agatoxins from Agelenopsis aperta (Funnel-web spider) are small disulphide rich polypeptides which are grouped in different classes according to their pharmacological properties against N, L and P/Q calcium currents. Some omega-agatoxins are very specific such as type I, II and IV omega-agatoxins, which respectively block L, N and P currents. Type III omega-agatoxins are less selective and block both N and L currents with the same potency. Type II and type III omega-agatoxins have clear similarity regarding the location of cysteine residues which have a C-x(6)-C-x(6,8)-C-x-C-C-x(5)-C arrangement [PMID: 11086219, PMID: 11711120].

The following spider toxins contain the same cysteine arrangement:

  • Agelenopsis aperta (funnel-web spider) omega-agatoxin (omega-Aga)-IIA, -IIIA, -IIIB, -IIIC and -IIID.
  • Phoneutria nigriventer (brazilian armed spider) omega-phonetoxin (omega- Ptx)-IIA and PNTx22C5 [PMID: 9683727].
  • Phoneutria reidyi (Brazilian Amazonian armed spider) neurotoxin PRTx18C2.
  • Ancylometes sp. (South American fishing spider) neurotoxin ANC32C7.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE patterns