Abstract
BackgroundToxin profiling helps in cataloguing the toxin present in the venom as well as in searching for novel toxins. The former helps in understanding potential pharmacological profile of the venom and evolution of toxins, while the latter contributes to understanding of novel mechanisms of toxicity and provide new research tools or prototypes of therapeutic agents.ResultsThe pygmy copperhead (Austrelaps labialis) is one of the less studied species. In this present study, an attempt has been made to describe the toxin profile of A. labialis from Kangaroo Island using the cDNA library of its venom glands. We sequenced 658 clones which represent the common families of toxin genes present in snake venom. They include (a) putative long-chain and short-chain neurotoxins, (b) phospholipase A2, (c) Kunitz-type protease inhibitor, (d) CRISPs, (e) C-type lectins and (f) Metalloproteases. In addition, we have also identified a novel protein with two Kunitz-type domains in tandem similar to bikunin.ConclusionInterestingly, the cDNA library reveals that most of the toxin families (17 out of 43 toxin genes; ~40%) have truncated transcripts due to insertion or deletion of nucleotides. These truncated products might not be functionally active proteins. However, cellular trancripts from the same venom glands are not affected. This unusual higher rate of deletion and insertion of nucleotide in toxin genes may be responsible for the lower toxicity of A. labialis venom of Kangroo Island and have significant effect on evolution of toxin genes.
Highlights
Toxin profiling helps in cataloguing the toxin present in the venom as well as in searching for novel toxins
We propose that the lower venom toxicity and subsequent decreased size of these snakes could be due to unusually high degree of deletions or insertions (~40%) in their toxin genes resulting in truncated, most likely inactive products
First strand cDNAs were synthesized from 150 ng of total RNA according to protocol of CreatorTM SMARTTM cDNA library construction kit obtained from Clontech Laboratories (Palo Alto, CA, USA)
Summary
Toxin profiling helps in cataloguing the toxin present in the venom as well as in searching for novel toxins. Only a small number of proteins have been isolated and characterized from A. superbus venom. Pigmy copperhead (A. labialis) is smaller in size as compared to A. superbus and A. ramsayi [7] and it has distinguishable white bars to its upper lips, circular eyes and yellowish-brown iris [8]. They mainly feed on small lizards and frogs [7] and the LD50 of their venom is 1.3 mg/kg [8]. We have attempted to profile venom components of A. labialis to define its composition and to look for novel proteins
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