Abstract.
The venoms of Australian snakes contain a myriad of pharmacologically active toxin components. This study describes the identification and comparative analysis of two distinct toxin families, the kunitztype serine protease inhibitors and waprins, and demonstrates a previously unknown evolutionary link between the two. Multiple cDNA and full-length gene isoforms were cloned and shown to be composed of three exons separated by two introns. A high degree of identity was observed solely within the first exon which coded for the propeptide sequence and its cleavage site, and indicates that each toxin family has arisen from a gene duplication event followed by diversification only within the portion of the gene coding for the functional toxin. It is proposed that while the mechanism of toxin secretion is highly conserved, diversification of mature toxin sequences allows for the existence of multiple protein isoforms in the venom to adapt to variations within the prey environment.
Electronic supplementary material
The online version of this article (doi:10.1007/s00018-008-8573-5) contains supplementary material, which is available to authorized users.
Keywords. Elapid, waprin, kunitz-like inhibitors, venom, toxin, gene
Electronic Supplementary material
Footnotes
Received 14 September 2008; received after revision 08 October 2008; accepted 09 October 2008
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