Functional, proteomic and transcriptomic characterization of the venom from Micrurus browni browni: identification of the first lethal multimeric neurotoxin in coral snake venom

Abstract

Proteomic characterization of Micrurus browni browni venom showed approximately 41 components belonging to 9 protein families, mainly phospholipases A2 (PLA2s) and three-finger toxins (3FTxs). Venom gland transcriptome yielded 39 venom transcripts belonging to 10 protein families. Functional characterization identified a multimeric toxin, here designated Brownitoxin-1, which comprises at least one PLA2 and one 3FTx. Its components have no or very low lethality individually but become extremely lethal when combined; both were partially characterized. Other two lethal components were identified: A neurotoxic PLA2, and a postsynaptic α-neurotoxin. LD50s as well as PLA2 and nAChR-blocking activities were determined for whole venom and isolated components. Application of venom to murine neuromuscular preparations caused a progressive decrease of twitch force that was irreversible after washing. Inhibition of PLA2 activity with p-bromophenacyl bromide (pBPB) showed that approximately 90% of toxicity is dependent on this activity. Non-lethal components include diverse 3FTxs, at least three enzymatically active PLA2s and the nociceptive toxin MitTx. No evidence of specificity towards prey was observed. This work is one of the most complete characterizations of a coral snake venom so far and its findings highlight the relevance of protein complexes in venom function.