Elapidae, toxins

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. 

Finally, venoms from different snakes from the Elapidae and Hydrophidae families also contain a cocktail of different paralytic toxins, some of which are selective for voltage-dependent Ca channels. For instance, the venom of the black mamba Dendroaspis polylepis polylepis contains a toxin termed calciseptine, which selectively blocks L-type Ca channels [6] and the venom from the green mamba D. agusticeps contains calcicludine, a toxin that acts as a potent blocker of most of the HVA Ca channels [7]. 

Bungarotoxins. Toxins of the very poisonous southeast Asian snake Bungarus multicinctus (striped krait, Elapidae). Crude extract of venom LD50 (mouse s.c.) 0.019 to 0.33 mg/kg. The postsynaptic neurotoxin a-B. is a polypeptide (Mr ca. 8000) of 74 amino acids and 5 disulfide bridges exhibiting curare-like activity. jS-B. contains different polypeptides and is a pre-synaptic neurotoxin. 

Fasciculins belong to the structural family of threefingered toxins from Elapidae snake venoms, which include the a-neurotoxins that block the nAChR and the cardiotoxins that interact with cell membranes. The features unique to the known primary and tertiary structures of the fasciculin molecule were analyzed by Flarald et al. (1995). Loop I contains an arginine at position 11, which is found only in the fasciculins and could form a pivotal anchoring point to AChE. Loop II contains five cationic residues near its tip, which are partly charge-compensated by anionic side chains in loop III. 

Cobra Venom Factor (CVF) is an unusual venom component known to be present in the venom of the cobra species Naja, Ophiophagus, and Hemachatus of the Elapidae family (1). CVF is not a toxin in the classical sense. As a matter of fact, the purified molecule is not toxic. It specifically interacts with components of the serum complement system, leading to complement activation which in turn leads to the consumption of complement activity. 

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