Crotoxin

Chang CC, Su MJ (1982) Presynaptic toxicity of the histidine-modified, phospholipase A2-inactive, beta-bungarotoxin, crotoxin and notexin. Toxicon 20 895-905... 

Chang CC, Lee JD, Eaker D, Lohlman J (1977) Short communications the presynaptic neuromuscular blocking action of taipoxin. A comparison with beta-bungarotoxin and crotoxin. Toxicon 15 571-6... 

Anadon, A., Martinez-Larranaga, M.R. (1985). Effects of crotoxin on autonomic neuromuscular transmission in the guinea-pig myenteric plexus and vas deferens. Toxicon 23 963-72. Arvidson, K.B., Valerio, L.G., Jr., Diaz, M., Chanderbhan, R.F. (2008). In silico toxicological screening of natural products. Toxicol. Mech. Meth. 18 229-42. 

Soybean trypsin inhibitor Tobacco mosaic virus Aldolase Crotoxin... 

Agent Index A278 Local effects from Crotoxin is a rapid- Obtained from... 

Basic polypeptide toxin from rattlesnake Crotalus terrificus. Activates sodium channels in muscle depolarization and contracture, blocked by tetrodotoxin. See also crotoxin. 

Toxins pre-synaptic neurotoxins, polypeptides, all chemically related to phospholipase A but no link between the phospholipase activity and toxicity. Effects similar to a-glycerotoxin and latrotoxin qv, e.g. crotoxin, notexin, taipoxin and (3-bungarotoxin. 

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... 

Crotoxin. Main component of the snake venoms of rattlesnakes (Crotalinae). It is a complex of a basic phospholipase A2 (C. B, Mr 13 500) with an acidic protein (C. A, Mr 10000) which transports the phospholipase to its site of action, the presynaptic membrane of the neuromuscular end-plates. Poisoning leads to local pain and necrosis. Systemic sequelae are tiredness, collapse, and shock through to death. In addition to the neurotoxicity, C. also has hemolytic action. 

Anaddn, A., Martinez-Larrahaga, M.R., 1985. Effects of crotoxin on autonomic neuromuscular transmission in the guinea-pig myenteric plexus and vas... 

One type of presynaptic toxin is composed of two subunits bound together. The basic subunit has phospholipase A activity, whereas the acidic subunit has no enzymic activity. Crotoxin is the first presynaptic toxin isolated from snake venom and is also one of the most well-studied presynaptic toxins. 

The role of the acidic subunit A is to guide the toxin to a specific site, then the basic subunit B functions as a presynaptic toxin (Hendon and Tu, 1979). Each subunit alone is relatively nontoxic, but combined, the toxicity is greatly enhanced (Trivedi et al., 1989). The undissociated crotoxin itself shows phospholipase A activity, indicating the active site of subunit B is not masked by subunit A (Radvanyi and Bon, 1984). Besides neurotoxicity, subunit B also has hemolytic activity. Subunit B attaches to many parts of the erythrocyte membranes (Jeng et al., 1978) and also on the postsynaptic membrane (Bon et al., 1979), in addition to the presynaptic binding site. 

Mojave toxin from Crotalus scutulatus is also structurally similar to crotoxin and is composed of two subunits (Bieber et al., 1975 Cate and Bieber, 1978). There are considerable amino acid sequence homologies between the two toxins (Aird et al., 1990). The amino acid sequence and spectroscopic properties of subunits of crotoxin are similar to other presynaptic phospholipases A from snake venoms (Aird et al., 1989a). 

Crotoxin s neurotoxic action is very similar to P-bungarotoxin (P-btx), but has some difference. For instance, crotoxin and its subunit B have a postsynaptic effect, whereas p-btx has no such activity (Bon et al., 1979). 

In P-btx, the A chain is the one that has phospholipase A activity The nomenclature is somewhat opposite that of crotoxin or Mojave toxin in crotoxin or Mojave toxin, subunit B is the one showing phospholipase A activity. Oxidation of methionine at the 6 and 8 positions lowered the toxicity without affecting antigenicity. Moreover, the NH2-terminal region of the A chain plays a crucial role in maintaining functional activity (Chang and Yang, 1988). 

Aird, S. D., Kaiser, 1.1., Lewis, R. V, and Kruggel, W. G. (1986). A complete amino acid sequence for the basic subunit of crotoxin. Arch. Biochem. Biophys. 249 296-300. 

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