Proteomic characterisation of the neurotoxic venoms of South Asian kraits and an assessment of drivers of venom variation.

Snake venoms are complex biochemical arsenals shaped by evolutionary processes such as ecological interactions, geographic variation, phylogenetic constraints, and ontogenetic changes. In South Asia, kraits of the genus Bungarus are medically important snakes, yet studies on venom composition and the drivers of venom variation remain limited. We analyzed the inter-specific and intra-specific venom composition of nineteen snakes belonging to five Bungarus species. Using a bottom-up proteomics approach involving RP-HPLC and tandem mass spectrometry we characterized the venom components into toxin families (TxFA) and functional classes (TxFU) and identified between 22 and 105 different toxin proteins in these venoms. The proteomes were dominated by phospholipase A2 and three-finger toxins, together constituting over 85 % of the total venom and were associated with pre- and post-synaptic neurotoxicity respectively. TxFU resolved the venom toxin composition better than TxFA for the five species. Intra-specific variation in venom composition in Bungarus caeruleus was not influenced by geographic distance. Inter-specific variation in venom composition in five Bungarus species was shaped by phylogeny rather than geography. This highlights the need for a regionally representative antivenoms that includes venoms of non-target krait species.