Sodium-channel-directed neurotoxins

Comparative structural analysis of sodium channel genes has permitted the development of testable hypotheses concerning the neurotoxin recognition properties of the sodium channel protein. However, specific elements of the deduced structure have not yet been definitively correlated with the molecular recognition of sodium channel-directed neurotoxins by discrete binding domains. It is, thus, not possible at the present time to know which pharmacological properties are determined by the sodium channel protein per se and which are determined by interactions between it and crucial features of its membrane environment. Clearly, it will be necessary to analyze the effects of specific modifications of sodium channel structure in a defined membrane environment in order to address these and other questions relating to sodium channel function. 

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... 

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