Meeting Abstract
Calcins are small peptides that bind to ryanodine receptors, which have been isolated only from the venom of the non-Buthidae scorpions. The physical-chemical properties, along with structure-function relationships, of the calcins are known from a limited sample of seven species in five families. Here, we conduct bioinformatic surveys of putative calcins orthologues using all available scorpion venom transcriptomes, including a newly sequenced transcriptome of the species Kololt magnus. We provide a comprehensive analysis of the structure of 39 putative calcins (from 35 species in 14 families), based on their primary sequence and their 3D structure models, using a new scorpion phylogenomic framework and morphometric tools. The reconstructed phylogeny of the full precursor of calcins mirrors the phylogenetic tree of the scorpions. Purifying selection is detected in 24 sites of the mature peptide sequence, whereas three codons are evolving under positive selection. Our morphometric analyses of the frontal and lateral surfaces of the 3D structures suggest divergence between calcins and the ICK calcin-like peptides from the buthid scorpion venom. Additionally, only two calcins exhibit major evolutionary shifts (detected under an Ornstein-Uhlenbeck model) in their 3D structures, net charge, molecular weight and volume. Our results demonstrate that calcins are the first molecular synapomorphy of the parvorder Iurida.
