Meeting Abstract
Rear-fanged snakes (“colubrids”) include a remarkable diversity of species that are found more broadly distributed than any other group of snakes, in part because of venom systems that are proving to be very diverse variants of a familiar theme. Among snake venoms, the three-finger toxins (3FTxs) are one of the better known families, with highly conserved structural scaffolds that supports a myriad of pharmacologies. For example, α-neurotoxins are potent blockers of motor endplate acetylcholine receptors, but structurally similar molecules are used by plethodontid salamanders in courtship and in limb regeneration. Snakes in the Asian genus Boiga produce numerous 3FTxs, and some of them, such as irditoxin, are dominant venom components with taxon-specific and potent neurotoxic effects directed toward lizard prey. This motif is turning out to be common among the rear-fanged Colubridae – New World Oxybelis also shows this pattern, and we have recently characterized a lizard-specific dimeric 3FTx, with high homology with irditoxin, in the venom of Spilotes sulfureus,. Like Boiga, the venom gland transcriptome of S. sulfureus, formerly considered to lack a Duvernoy’s venom gland, is dominated by 3FTxs, and the expressed venom consists of >92% 3FTxs, higher even than the vast majority of elapid venoms. However, in addition to a lizard-specific 3FTx, S. sulfureus venom also contains a mammal-specific monomeric neurotoxin, sulmotoxin, which is non-toxic to lizards. This is a unique toxin among 3FTxs and snake venoms generally, and it illustrates further the extent to which selection has favored diversification of a single toxin scaffold among snake venoms. Our results clearly demonstrate that a diversity of novel structural and functional variants of familiar toxins exist among rear-fanged colubrids.
