Pompilidotoxin is a toxin from the venom of spider wasps that slows the inactivation of Na+channels.
Contents
Etymology
Pompilidotoxin is named after the pompilidae wasp family (commonly called spider wasps).
Chemistry
Structure α-PMTX consists of 13 amino acid residues with the sequence Arg-Ile-Lys-Ile-Gly-Leu-Phe-Gln-Asp-Leu-Ser-Lys-Leu-NH2.
Replacement of the lysine residue at position 12 of α-PMTX with arginine results in β-PMTX.
Homology α-PMTX has no structural homology with other toxins. It lacks disulfide bonds which are known to be present in other toxins acting on sodium channels, such as sea anemone toxins or scorpion toxins.
Target
Both α- and β-PMTX slow the inactivation of neuronal sodium channels (but not heart sodium channels), possibly by binding to the neurotoxin receptor site 3 on the extracellular surface of the sodium channel.
β-PMTX has higher potency than α-PMTX.
Mode of action
By slowing down the inactivation of sodium channels, PMTXs can potentiate synaptic transmission in the lobster neuromuscular endplate.