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First Protein Toxin in Amphibians Identified

The first gene-encoded protein toxin in an amphibian has been identified by researchers in China. The toxin, named anntoxin, is a 60-amino-acid neurotoxin found in the skin of a Chinese tree frog, Hyla annectans. The discovery may help shed light on the evolution of toxins. While gene-encoded protein toxins have been identified in many vertebrate animals, including fish, reptiles, and mammals, none has previously been found in amphibians or birds. In the case of poisonous amphibians, like the tropical poison dart frogs, their toxins are usually small chemicals like alkaloids that are extracted from insects and secreted onto the animal's skin. In protein sequence and structure, anntoxin is very similar to dendrotoxins (the venoms found in cobras and other mamba snakes) and cone snail toxins. Like these other toxinx, anntoxin is fast-acting and potent; the researchers found it could produce rapid convulsions, paralysis, and respiratory distress in several would-be predators such as snakes and birds. The discovery of anntoxin was reported in the August 14 issue of the Journal of Biological Chemistry. [Press release] [JBC abstract]