Insights into the subunit arrangement and diversity of paradoxin and taipoxin

Paradoxin and taipoxin are neurotoxic phospholipases from the inland and coastal species of Australian taipan. Despite their relatively high sequence homology of 70% and 84% for the acidic and basic chains respectively, they differ substantially in reported assays of neurotoxicity. This study provides the first characterisation of paradoxin, which like taipoxin, is a trimer at physiological pH. More broadly, these toxins were found to be composed of a more diverse range of subunits than previously recognised, including newly discovered γTPx isoforms, which give rise to an additional, major conformation of TPx.