Neurotoxins from snake venoms

Neurotoxins from snake venoms have proved to be valuable tools for the understanding of synaptic transmission mechanisms. Likewise, the powerful inhibitory action of fasciculins against mammalian AChE makes them potentially useful for pharmacological and neurochemical research. Studies of their biochemical and electrophysiological effects on the CNS and biochemical characterization are now being carried out. 

Endo, T. and Tamiya, N. (1991) Structure-function relationships of postsynaptic neurotoxins from snake venoms, in Snake Toxins " (Harvey, A.L., ed.) Pergamon Press, New York, pp. 165-222. 

Endo T., Oya, M., Tamiya, N. and Hayashi, K. (1987) Role of C-terminal tail of long neurotoxins from snake venoms in molecular conformation and acetylcholine receptor binding Protein nuclear magnetic resonance and competition binding studies. Biochemistry 26 4592-4598. 

Chen, J., Wu, X., Zhang, G., Jiang, M. and Hsu, K. (1981) Further purification and biochemical properties of a pre-synaptic neurotoxin from snake venom of Agkistrodon halys (Pallas). Acta Biochim. Biophys. 

The similarity of the primary structure of different sea snake venoms has already been discussed. Postsynaptic neurotoxins from Elapidae venom have been extensively studied. Elapidae include well-known snakes such as cobra, krait, mambas, coral snakes, and all Australian snakes. Like sea snake toxins, Elapidae toxins can also be grouped into short-chain (Type I) and long-chain (Type II) toxins. Moreover, two types of neurotoxins are also similar to cardiotoxins, especially in the positions of disulfide bonds. However, amino acid sequences between cardiotoxins and sea snake and Elapidae neurotoxins are quite different. In comparing the sequence of sea snake and Elapidae neurotoxins, there is a considerable conservation in amino acid sequence, but the difference is greater than among the various sea snake toxins. 

Abe T, Alemd S, Miledi R (1977) Isolation and characterization of presynaptically acting neurotoxins from the venom of bungarus snakes. Eur J Biochem 80 1-12... 

Pearson JA, Tyler MI, Retson KV, Howden ME (1993) Studies on the subunit structure of tex-tilotoxin, a potent presynaptic neurotoxin from the venom of the australian common brown snake (pseudonaja textilis). 3. the complete amino-acid sequences of all the subunits. Biochem Biophys Acta 1161 223-9... 

Such interactions with other membrane components could certainly provide an attractive basis for the specificity of some peptides that appear to have a similar general structure. This situation might then be analogous to that of a group of structurally related peptides from snake venom which have separate defined regions that are responsible for either cytotoxicity or neurotoxin activity 28),... 

Aird, S. D., Middaugh, C. R., and Kaiser, I. I. (1989b). Spectroscopic characterization of textilotoxin, a presynaptic neurotoxin from the venom of the Australian eastern brown snake (Pseudonaja t. textilis). Biochim. Biophys. Acta 997 219-223. 

Halpert, J. and Eaker, D. Amino acid sequence of a presynaptic neurotoxin from the venom of Notechis scutatus scutatus (Australian tiger snake). 250 6990-6997, 1975. 

Neurotoxins from Sea Snake and Other Vertebrate Venoms... 

All sea snakes are poisonous and their venoms are extremely toxic. The LD q for crude sea snake venom can be as low as 0.10 fig/g mouse body weight (i). For purified toxin the LD q is even lower, suggesting the high toxicity of sea snake toxins and venoms. This toxicity is derived from the presence of potent neurotoxins. Compared to snake venoms of terrestrial origin, sea snake venoms have been studied less. Different enzymes reported to be present or absent are summarized in Table I. 

Neurotoxin obtained from the venom of the Australian taipan snake. 

Lee CY, Chang CC, Chen YM (1972) Reversibility of neuromuscular blockade by neurotoxins from elapid and sea snake venoms. Taiwan Yi Xue Hui Za Zhi 71 344-9 Lee CY, Tsai MC, Chen YM, Ritonja A, Gubensek F (1984) Mode of neuromuscular blocking action of toxic phospholipases A2 from vipera ammodytes venom. Arch Int Pharmacodyn Ther 268 313-24... 

Short Neurotoxins. The 58 snake venom short neurotoxins submitted to analysis are presented in Table II. This data base, which contains 27 inactive and 30 active toxins, was built from data reported by Karlsson (11) and Dufton et al. (12). 

Even snake venom has been tried. Called crotoxins, from the genus Crotalus, one of the two genera for rattlesnakes, these are neurotoxins that were found to have some sort of anticancer effect, direct or indirect, but presumably in very small concentrations. The snake in particnlar was said to be the cascabel, or Crotalus... 

Most venoms are mixtures of dozens of compounds, and the active toxic ingredients are proteins that wreak havoc on the recipient in a variety of ways. While the exact enzymes vary from species to species, and even geographically within a species, many snake venoms contain some sort of neurotoxins which block signals sent through your nervous system, leading to numbness or even paralysis. 

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