Fig. 6.

Secreted proteins evolve rapidly, and more abundant venom toxins evolve most rapidly of all. a Violin plot of evolutionary rates of secreted proteins (those detected by mass spectrometry in the venom) vs. the rest of the transcriptome. Secreted proteins evolve significantly faster than the rest of the transcriptome, suggesting that they are subject to atypically strong selection within the genome. b Relationship between abundance and nucleic acid evolutionary rate for secreted proteins. More abundant venom components, which likely represent a greater metabolic investment for the snake, but are also more likely to contribute to the venom’s effectiveness, evolve faster. Abbreviations: 5′NT 5′-nucleotidase, CTL C-type lectin, LAO L-amino acid oxidase, MP metalloprotease, PDE phosphodiesterase, PLA phospholipase, SP serine protease, QC glutaminyl-peptide cyclotransferase. Several unlabeled points represent proteins present in the venom at low concentrations, but without clear pharmacological significance