Wednesday, March 14, 2012

Tiger Rattlesnake Venom, Lethal and Neurotoxic, Yet Simple

Crotalus tigris. JCM
Tiger rattlesnakes, Crotalus tigris, are relatively small (< 90cm), and geographically restricted to south-central Arizona (USA), northwestern Sonora (Mexico), and Isla Tiburón in the Gulf of California (Mexico). However they have been considered to produce the most lethal venom of any snake in the western hemisphere. Toxicological and immunology assays done in the early 1990’s suggested a neurotoxic component was present in its venom, and Mojave toxin was suspected to be the neurotoxic molecule present. Now, Calvette et al. (2012) have characterized Crotalus tigris venom and found tiger rattlesnakes to have the highest lethality for mice among rattlesnakes but the simplest toxin proteome reported to date; describing the venom proteome as “minimalist.” The venom proteins of C. tigris comprises 7–8 gene products from 6 toxin families, including the presynaptic β-neurotoxic heterodimeric PLA2, Mojave toxin, and two serine proteinases comprise, respectively, 66 and 27% of the C. tigris toxin arsenal. Other molecules included a VEGF-like protein, a CRISP molecule, a medium-sized disintegrin, and 1–2 PIII-SVMPs and each represented 0.1–5% of the total venom proteome. The authors suggest that the toxin profile explains the systemic neurotoxic and myotoxic effects observed in envenomated animals exceptionally well. They also found venom lethality of C. tigris and other North American rattlesnake type II venoms correlates with the concentration of Mojave toxin A-subunit, supporting the view that the neurotoxic venom phenotype of crotalid type II venoms may be described as a single-allele adaptation. They also suggest that the trend toward neurotoxicity, also reported for the South American rattlesnakes, may have evolved by pedomorphism, and that the development of a pan-American antivenom for all rattlesnakes may be possible.

Calvete, JJ, Perez, A., Lomontes, B., Sanchez, E., and Sanz, L. 2012. Snake Venomics of Crotalus tigris: The Minimalist Toxin Arsenal of the Deadliest Neartic Rattlesnake Venom. Evolutionary Clues for Generating a Pan-Specific Antivenom against Crotalid Type II Venoms. Journal of Proteome Research 11, 1382-1390

1 comment:

  1. Ah! An excellent article describing the venom components of this exceptionally toxic snake. Around 0.06 mgm will kill a mouse. If a human is bitten, the question becomes: will you die like a man or die like a mouse? Ha!Ha! No laughing matter, if bitten, seek professional medical help immediately.