Proteomic studies on Micrurus (coral snakes) venom reveal a dichotomy of phenotypes

Abstract

Background: Nearly half of extant snake species, mainly within the Viperidae and Elapidae families, produce venom secretions of variable toxicities. The application of proteomic tools to the study of these venoms has led to an impressive growth in knowledge about their composition, toxicity, and immunogenicity. About one-third of all 'venomic' studies have focused on elapid species, mainly those inhabiting the Old World. The New World elapids, represented by coral snakes, have been less studied due the more limited availability of their venoms, owing to their difficult maintenance in captivity and very low venom yields. Method: In recent years, however, a number of venomic studies on Micrurus species from North, Central, and South America have been conducted, thanks to the increasing sensitivity of proteomic tools. Results/Discussion: Some general trends and patterns concerning the compositional, functional, and immunological characteristics of Micrurus venoms are emerging from such studies. Results gathered to date, encompassing about one-third of the >70 species of Micrurus, have revealed a dichotomy of venom phenotypes regarding the relative abundance of the omnipresent phospholipases A2 (PLA2) and 'three-finger' toxins (3FTx): some species express a PLA2-predominant venom composition, while others display a 3FTx-predominant compositional pattern. These two sharply divergent toxin expression patterns appear to be related to phylogenetic positions and geographical distributions along a North-South axis, but further venom studies encompassing a higher number of species will be relevant to assess this hypothesis. The two venom phenotypes also show correlations to some toxic functionalities, complexity in the diversity of proteoforms, and immunological cross-recognition patterns. Based on the known (but partial) phylogenies, we have proposed the 3FTx-rich venom phenotype to be the ancestral state, with PLA2-preponderant venoms appearing in more derived species. Conclusions: Understanding the dichotomy of venom compositions within Micrurus snakes, observed in some cases even among sympatric species that inhabit relatively small geographic areas, with probable similar diets, remains a challenging area of research.