Pompilidotoxin is a

toxin A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849– ...

from the venom of

spider wasp Wasps in the family Pompilidae are commonly called spider wasps, spider-hunting wasps, or pompilid wasps. The family is cosmopolitan, with some 5,000 species in six subfamilies. Nearly all species are solitary (with the exception of some group-ne ...

s that slows the inactivation of Na⁺channels.

Etymology

Pompilidotoxin is named after the

pompilidae Wasps in the family Pompilidae are commonly called spider wasps, spider-hunting wasps, or pompilid wasps. The family is cosmopolitan, with some 5,000 species in six subfamilies. Nearly all species are solitary (with the exception of some group-ne ...

wasp family (commonly called spider wasps).

Sources

α-Pompilidotoxin (α-PMTX) can be extracted from the venom of a solitary wasp, ''

Anoplius ''Anoplius'' is a genus of spider wasps in the family Pompilidae, called the blue-black spider wasps. The genus includes the following species: *'' Anoplius aethiops'' (Cresson 1865) *'' Anoplius americanus'' (Beauvois) *'' Anoplius amethystinu ...

samariensis''. β-Pompilidotoxin (β-PMTX) originates from the venom of another wasp, ''

Batozonellus ''Batozonellus'' is a genus of the spider hunting wasps (insects belonging to the family Pompilidae). Description The species of the genus ''Batozonellus'' range from large to very large. Body is black and yellow. The compound eyes are large. Cl ...

maculifrons''.

Chemistry

''Structure'' α-PMTX consists of 13

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

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 Homology may refer to: Sciences Biology *Homology (biology), any characteristic of biological organisms that is derived from a common ancestor * Sequence homology, biological homology between DNA, RNA, or protein sequences *Homologous chrom ...

with other toxins. It lacks

disulfide bond In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In ...

s which are known to be present in other toxins acting on sodium channels, such as

sea anemone Sea anemones are a group of predation, predatory marine invertebrates of the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemones are classifi ...

toxins or

scorpion Scorpions are predatory arachnids of the order Scorpiones. They have eight legs, and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always end ...

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 Receptor may refer to: * Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a ...

site 3 on the

extracellular This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms. It is intended as introductory material for novices; for more specific and technical definitions ...

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.

References

*{{cite journal , vauthors=Kawai N, Konno K , title=Molecular determinants of two neurotoxins that regulate sodium current inactivation in rat hippocampal neurons , journal=Neurosci. Lett. , volume=361 , issue=1–3 , pages=44–6 , year=2004 , pmid=15135889 , doi=10.1016/j.neulet.2004.01.006, s2cid=38819369 Ion channel toxins