A further elucidation of the venom proteome of Australian Elapid Pseudechis australis

The Pseudechis genus (black snakes) occurs throughout mainland Australia and Papua New Guinea, with the most widespread species being P. australis (Mulga snake). Black snakes in Australia are known to have a significant number of phospholipase A2 (PLA2) toxins, with ten previously being identified. P. colletti (Collett’s snake) and P. papuanus (Papuan black snake) both have PLA2-dominant venoms, with more than 90% of the whole venom being PLA2. This is consistent with in vitro studies demonstrating high PLA2 activity in the genus. We aimed to characterise the venom proteome of P. australis with a two-dimensional fractionation method involving reverse-phase high-performance liquid chromatography and sodium dodecyl sulfate polyacrylamide gel electrophoresis alongside bottom-up proteomics. After matching the venom peptides to the transcriptome, we characterised 98% of the venom and found that 89.8% was PLA2, and the remainder of the venom consisted of only three other protein families, snake venom metalloprotease (SVMP), l-amino acid oxidase (LAAO) and triosephosphate isomerase, which made up 6.0%, 2.5% and 0.03% of the whole venom, respectively. LAAO usually occurs in abundances less than 1.6% in snake venoms worldwide, except in Hoplocephalus stephensii, another Australian elapid, making it the second highest abundance in Australian snake venoms. In addition, the presence of SVMP was unusual for an elapid, again consistent with other Australian elapids. We identified eleven different PLA2 toxins in the venom of P australis, but the other three protein families all had one toxin. The study again demonstrates the unusual characteristics of the venoms of Australian snake venoms, and in particular the PLA2-dominant venom of the genus Pseudechis, consistent with its clinical effects of myotoxicity and anticoagulant activity.