Ion channel toxins

Tetrodotoxin (TTX) is a potent neurotoxin. Its name derives from Tetraodontiformes, an order that includes pufferfish, porcupinefish, ocean sunfish, and triggerfish; several of these species carry the toxin. Although tetrodotoxin was discovered in these fish, it is found in several other animals (e.g., in blue-ringed octopuses, rough-skinned newts, and moon snails). It is also produced by certain infectious or symbiotic bacteria like Pseudoalteromonas, Pseudomonas, and Vibrio as well as other species found in symbiotic relationships with animals and plants.

Batrachotoxin (BTX) is an extremely potent cardiotoxic and neurotoxic steroidal alkaloid found in certain species of beetles, birds, and frogs. The name is from the Greek word . Structurally-related chemical compounds are often referred to collectively as batrachotoxins. In certain frogs, this alkaloid is present mostly on the skin. Such frogs are among those used for poisoning darts. Batrachotoxin binds to and irreversibly opens the sodium channels of nerve cells and prevents them from closing, resulting in paralysis and death. No antidote is known.

Maitotoxin (MTX) is an extremely potent toxin produced by Gambierdiscus toxicus, a dinoflagellate species. Maitotoxin has been shown to be more than one hundred thousand times as potent as the nerve agent VX. Maitotoxin is so potent that it has been demonstrated that an intraperitoneal injection of 130 ng/kg was lethal in mice. Maitotoxin was named from the ciguateric fish Ctenochaetus striatus—called "maito" in Tahiti—from which maitotoxin was isolated for the first time. It was later shown that maitotoxin is actually produced by the dinoflagellate Gambierdiscus toxicus.

Grayanotoxins are a group of closely related neurotoxins named after Leucothoe grayana, a plant native to Japan and named for 19th-century American botanist Asa Gray. Grayanotoxin I (grayanotoxane-3,5,6,10,14,16-hexol 14-acetate) is also known as andromedotoxin, acetylandromedol, rhodotoxin and asebotoxin. Grayanotoxins are produced by Rhododendron species and other plants in the family Ericaceae. Honey made from the nectar and so containing pollen of these plants also contains grayanotoxins and is commonly referred to as mad honey.

thumb|Unlike the typical 6-6-6-5 steroid ring backbone (1), veratridine displays a 6-6-5-6 arrangement (2).Veratridine is a steroidal alkaloid found in plants related to lilies, specifically the genera Veratrum and Schoenocaulon. Upon absorption through the skin or mucous membranes, it acts as a neurotoxin by binding to and preventing the inactivation of voltage-gated sodium ion channels in heart, nerve, and skeletal muscle cell membranes. Veratridine increases nerve excitability and intracellular Ca2+ concentrations.

thumb|300px|right|class=skin-invert-image|Chemical structure of the ciguatoxin CTX1B Ciguatoxins are a class of toxic polycyclic polyethers found in fish that cause ciguatera.

A conotoxin is one of a group of neurotoxic peptides isolated from the venom of the marine cone snail, genus Conus.

Tinyatoxin (TTX or TTN) is an analog of the neurotoxin resiniferatoxin. It occurs naturally in Euphorbia poissonii.

Apamin is an 18 amino acid globular peptide neurotoxin found in apitoxin (bee venom). Dry bee venom consists of 2–3% of apamin. Apamin selectively blocks SK channels, a type of Ca2+-activated K+ channel expressed in the central nervous system. Toxicity is caused by only a few amino acids, in particular cysteine1, lysine4, arginine13, arginine14 and histidine18. These amino acids are involved in the binding of apamin to the Ca2+-activated K+ channel. Due to its specificity for SK channels, apamin is used as a drug in biomedical research to study the electrical properties of SK channels and thei

Dendrotoxins are a class of presynaptic neurotoxins produced by mamba snakes (Dendroaspis) that block particular subtypes of voltage-gated potassium channels in neurons, thereby enhancing the release of acetylcholine at neuromuscular junctions. Because of their high potency and selectivity for potassium channels, dendrotoxins have proven to be extremely useful as pharmacological tools for studying the structure and function of these ion channel proteins. thumb|3D model of α-dendrotoxin. colored in red are positively charged amino acid residues in the N-terminus and the β-turn region that are b

Chlorotoxin is a 36-amino acid peptide found in the venom of the deathstalker scorpion (Leiurus quinquestriatus) which blocks small-conductance chloride channels. The fact that chlorotoxin binds preferentially to glioma cells has allowed the development of methods for the treatment and diagnosis of several types of cancer.

Myotoxins are small, basic peptides found in snake venoms (e.g. rattlesnakes) and lizard venoms (e.g. Mexican beaded lizard). This involves a non-enzymatic mechanism that leads to severe muscle necrosis. These peptides act very quickly, causing instantaneous paralysis to prevent prey from escaping and eventually death due to diaphragmatic paralysis.

α-Bungarotoxin is one of the bungarotoxins, components of the venom of the elapid Taiwanese banded krait snake (Bungarus multicinctus). It is a type of α-neurotoxin, a neurotoxic protein that is known to bind competitively and in a relatively irreversible manner to the nicotinic acetylcholine receptor found at the neuromuscular junction, causing paralysis, respiratory failure, and death in the victim. It has also been shown to play an antagonistic role in the binding of the α7 nicotinic acetylcholine receptor in the brain, and as such has numerous applications in neuroscience research.

Bungarotoxins are toxins found in the venom of snakes and kraits. Bites from these animals can result in severe symptoms including bleeding or hemorrhage, paralysis and tissue damage that can result in amputation. The paralytic effects of venom are particularly dangerous as they can impair breathing. These symptoms are the result of bungarotoxin presence in the venom. In actuality, venom contains several distinct bungarotoxins, each varying in which receptors they act on and how powerful they are.

Philanthotoxins are components of the venom of the Egyptian solitary wasp Philanthus triangulum, commonly known as the European beewolf. Philanthotoxins are polyamine toxins, a group of toxins isolated from the venom of wasps and spiders which immediately but reversibly paralyze their prey. δ-philanthotoxin, also known as PhTX-433, is the most active philanthotoxin that can be refined from the venom. PhTX-433 functions by non-selectively blocking excitatory neurotransmitter ion channels, including nicotinic acetylcholine receptors (nAChRs) and ionotropic glutamate receptors (iGluRs). Synthetic

Brevetoxin (PbTx), or brevetoxins, are a suite of cyclic polyether compounds produced naturally by a species of dinoflagellate known as Karenia brevis. Brevetoxins are neurotoxins that bind to voltage-gated sodium channels in nerve cells, leading to disruption of normal neurological processes and causing the illness clinically described as neurotoxic shellfish poisoning (NSP). Although brevetoxins are most well-studied in K. brevis, they are also found in other species of Karenia and at least one large fish kill has been traced to brevetoxins in Chattonella.

Slotoxin is a peptide from Centruroides noxius Hoffmann scorpion venom. It belongs to the short scorpion toxin superfamily.

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β-Bungarotoxin is a form of bungarotoxin that is fairly common in Krait (Bungarus multicinctus) venoms. It is the prototypic class of snake β-neurotoxins. There are at least five isoforms, coded β1 to β5, assembled from different combinations of A and Bchains.

Poneratoxin is a paralyzing neurotoxic peptide made by the bullet ant Paraponera clavata. It prevents inactivation of voltage gated sodium channels and therefore blocks synaptic transmission in the central nervous system. Specifically, poneratoxin acts on voltage gated sodium channels in skeletal muscle fibers, causing paralysis, and nociceptive fibers, causing pain. It is rated as a 4 plus on the Schmidt sting pain index, the highest possible rating with that system, and its effects can cause waves of pain up to twelve hours after a single sting. It is additionally being studied for its uses

Iodoresiniferatoxin (I-RTX) is a strong competitive antagonist of the Transient Receptor Potential Vanilloid 1 (TRPV1) receptor. I-RTX is derived from resiniferatoxin (RTX).

Calcicludine (CaC) is a protein toxin from the venom of the green mamba that inhibits high-voltage-activated calcium channels, especially L-type calcium channels.