Qualitative and Quantitative Proteomic Analysis of Venoms from Mexican Rattlesnakes

Despite the vast biodiversity of Mexican vipers, venom of endemic species has been barely studied. Here we analyzed the venom composition of three endemic species of rattlesnakes: Crotalus aquilus, C. triseriatus, and C. ravus. We used quantitative chromato-mass-spectrometry and compared venoms with C. molossus, a species commonly found in North America, in a comparative and phylogenetic framework. In total, we identified 165 proteins grouped in 19 main protein families, consistent with previous reports for viperid venoms. In C. aquilus and C. triseriatus, the most predominant protein-family type was Serine Proteases, and in C. triseriatus and C. molossus it was Snake Venom Metalloproteases. The Label-free quantification revealed a high proportion of Snake Venom Metalloproteases in C. aquilus, C. triseriatus, and C. molossus, reaching 28-47% of the total venom. In contrast, in C. ravus 47% of the venom was composed of Phospholipases A₂. Among the four species analyzed, C. triseriatus and C. aquilus were most similar in compositional profiles and their profiles are highly correlated. Venom composition in terminal clades and taxa were better explained by protein losses than evolution of new proteins. The triseriatus group share seven proteins, while the clade C. aquilus + C. triseriatus share seven derived protein features, of which six are protein losses.