PhTx-2 is a toxic fraction of the venom of the Brazilian wandering spider '' Phoneutria nigriventer''.

Target

This fraction is responsible for most of the venom's effects, acts on

voltage-gated ion channels Voltage-gated ion channels are a class of transmembrane proteins that form ion channels that are activated by changes in the electrical membrane potential near the channel. The membrane potential alters the conformation of the channel proteins, ...

, this fraction is composed of nine different

peptides Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A p ...

, of which PhTx-2-5 and PhTx-2-6 activate voltage-gated ion channels. PhTx-2 has been shown to be related to the activation and delay of inactivation of neuronal sodium channels, leading to an increase in the concentration of neuronal Ca++ and the release of

glutamate Glutamic acid (symbol Glu or E; the ionic form is known as glutamate) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can syn ...

, resulting in the release of neurotransmitters such as

acetylcholine Acetylcholine (ACh) is an organic chemical that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Part ...

and

catecholamines A catecholamine (; abbreviated CA) is a monoamine neurotransmitter, an organic compound that has a catechol (benzene with two hydroxyl side groups next to each other) and a side-chain amine. Catechol can be either a free molecule or a substi ...

.{{Cite book, last1=Weiss, first1=Marcelo Barros, url=https://books.google.com/books?id=NzlyDwAAQBAJ&q=PhTx-2+convuls%C3%B5es+paralisias&pg=PT161, title=Acidentes com Animais Peçonhentos, last2=Paiva, first2=Jorge Wilson Souza, date=2018-10-10, publisher=Thieme Revinter Publicações LTDA, isbn=978-85-5465-084-1, language=pt-BR

Primates Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...

are more sensitive to the PhTx-1 & 2 components than in the case of

mice A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...

, about 4 to 5 times more sensitive. The LD50 for a 70kg adult human is 6.3 mg, but the spider has only 1-2 mg and usually delivers 0.4 mg.

References

Toxicology