Potassium channel binding neurotoxins

C. Potassium Channel-Binding Neurotoxins. The potassium channel plays an important role in the repolarization process in nerve transmission and is less well known than the sodium channels in the nerve. The The channel is composed of membrane protein and has six transmembrane helical regions. Both the NHz- and COOH-terminal chains are located inside the membrane. The first snake toxin found to bind is dendrotoxin. This toxin is a potent convulsant and facilitates transmitter release by inhibition of voltage-sensitive channels (Weller et al., 1985 Penner et al., 1986 Harvey and Karlsson, 1980 Black... 

Neurotoxins of scorpions especially represent ion channel toxins that mainly affect sodium and potassium channels. Several compounds represent neurotoxins that are directed selectively against insects.97 Na+ channel-specific a-, (3-, and 7-toxins are composed of 58-76 amino acids and contain four stabilizing disulfide bridges.98 The well-studied K+ channel-specific toxins (divided into at least nine distinct peptide subfamilies) bind to the extracellular face of the channel and comprise 29-39 amino acids stabilized by 3-4 disulfide bridges.99 Various Ca2+ channel scorpion toxins, antimicrobial peptides, and short insectotoxins active on Cl channels have been found.96... 

Tetrodotoxin 17, produced by a number of marine organisms, including puffer fish and other members of Tetraodontiformes, is a potent neurotoxin that is approximately ten times more poisonous than potassium cyanide. It too blocks the action potential in nerves by binding to the voltage-gated, fast sodium channels in nerve cell membranes thereby preventing the nerve cells from firing. 

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