Transcriptomic analysis of the venom gland of the red-headed krait (Bungarus flaviceps) using expressed sequence tags

Ang Swee Siang,R Manjunatha Kini,Robin Doley,Freek J Vonk

doi:10.1186/1471-2199-11-24

Abstract

BackgroundThe Red-headed krait (Bungarus flaviceps, Squamata: Serpentes: Elapidae) is a medically important venomous snake that inhabits South-East Asia. Although the venoms of most species of the snake genus Bungarus have been well characterized, a detailed compositional analysis of B. flaviceps is currently lacking.ResultsHere, we have sequenced 845 expressed sequence tags (ESTs) from the venom gland of a B. flaviceps. Of the transcripts, 74.8% were putative toxins; 20.6% were cellular; and 4.6% were unknown. The main venom protein families identified were three-finger toxins (3FTxs), Kunitz-type serine protease inhibitors (including chain B of β-bungarotoxin), phospholipase A2 (including chain A of β-bungarotoxin), natriuretic peptide (NP), CRISPs, and C-type lectin.ConclusionThe 3FTxs were found to be the major component of the venom (39%). We found eight groups of unique 3FTxs and most of them were different from the well-characterized 3FTxs. We found three groups of Kunitz-type serine protease inhibitors (SPIs); one group was comparable to the classical SPIs and the other two groups to chain B of β-bungarotoxins (with or without the extra cysteine) based on sequence identity. The latter group may be functional equivalents of dendrotoxins in Bungarus venoms. The natriuretic peptide (NP) found is the first NP for any Asian elapid, and distantly related to Australian elapid NPs. Our study identifies several unique toxins in B. flaviceps venom, which may help in understanding the evolution of venom toxins and the pathophysiological symptoms induced after envenomation.

Highlights

The Red-headed krait (Bungarus flaviceps, Squamata: Serpentes: Elapidae) is a medically important venomous snake that inhabits South-East Asia
The other toxin families are less well presented; clones encoding phospholipase A2 (PLA2) (6.26% including A chains of β-bungarotoxin), and two clones each of natriuretic peptide (NP), cysteine-rich secretory protein (CRISPs), and C-type lectin (Figure 1B). 3FTx is the major transcript of this venom gland library constituting 39.29% of the toxin transcripts
Similar observation was made in Micrurus corallines venom gland library which belongs to the elapid family where the 3FTx constitutes ~52% of the toxin transcripts [12]

Summary

Introduction

The Red-headed krait (Bungarus flaviceps, Squamata: Serpentes: Elapidae) is a medically important venomous snake that inhabits South-East Asia. Snake venom is a complex mixture of biologically active proteins and peptides that exert very powerful and specific effects This mixture is interesting from the angle of molecular evolution, as the genes encoding the venom ingredients seem to undergo some form of hypermutation resulting in accelerated evolution and a staggering diversity of isoforms [1,2], sometimes functionally and structurally radically different. The basis for this phenomenon seems to be due to gene-duplication and diversification of existing venom genes. Snake venom is a valuable resource for proteins and peptides that may

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Conclusion