Abstract
BackgroundColombia and Brazil are affected by severe cases of scorpionism. In Colombia the most dangerous accidents are caused by Tityus pachyurus that is widely distributed around this country. In the Brazilian Amazonian region scorpion stings are a common event caused by Tityus obscurus. The main objective of this work was to perform the molecular cloning of the putative Na+-channel scorpion toxins (NaScTxs) from T. pachyurus and T. obscurus venom glands and to analyze their phylogenetic relationship with other known NaScTxs from Tityus species.Methodology/Principal FindingscDNA libraries from venom glands of these two species were constructed and five nucleotide sequences from T. pachyurus were identified as putative modulators of Na+-channels, and were named Tpa4, Tpa5, Tpa6, Tpa7 and Tpa8; the latter being the first anti-insect excitatory β-class NaScTx in Tityus scorpion venom to be described. Fifteen sequences from T. obscurus were identified as putative NaScTxs, among which three had been previously described, and the others were named To4 to To15. The peptides Tpa4, Tpa5, Tpa6, To6, To7, To9, To10 and To14 are closely related to the α-class NaScTxs, whereas Tpa7, Tpa8, To4, To8, To12 and To15 sequences are more related to the β-class NaScTxs. To5 is possibly an arthropod specific toxin. To11 and To13 share sequence similarities with both α and β NaScTxs. By means of phylogenetic analysis using the Maximum Parsimony method and the known NaScTxs from Tityus species, these toxins were clustered into 14 distinct groups.Conclusions/SignificanceThis communication describes new putative NaScTxs from T. pachyurus and T. obscurus and their phylogenetic analysis. The results indicate clear geographic separation between scorpions of Tityus genus inhabiting the Amazonian and Mountain Andes regions and those distributed over the Southern of the Amazonian rainforest. Based on the consensus sequences for the different clusters, a new nomenclature for the NaScTxs is proposed.
Highlights
Scorpion venoms are a rich mixture of several components, among which are free nucleotides, lipids, biogenic amines, proteins and peptides
This study reports for the first time the molecular cloning of the Na+-channel scorpion toxins (NaScTxs) precursors from T. pachyurus and T. obscurus scorpions by means of cDNA library constructions of their venom glands, presenting new putative NaScTxs and the precursor sequences of some Na+-channel peptides already described from previous proteomic researches with these two scorpion venoms [23,25,28,29]
Phylogenetic analysis with Tityus NaScTxs was done to infer whether the geographic separation between the scorpions of Tityus genus living in the North and South of the Amazon region led to evolutionary changes in these sequences
Summary
Scorpion venoms are a rich mixture of several components, among which are free nucleotides, lipids, biogenic amines, proteins and peptides. Scorpion peptides can be classified into disulfidebridged (DBPs) and non-disulfide-bridged peptides (NDBPs). DBPs are considered the main molecules responsible for the neurotoxic effects observed in scorpion envenoming as they affect ion-channels function of excitable and non-excitable cells. The best known DBPs are those specific for Na+ or K+ channels (NaScTxs and KTxs, respectively) [2,3]. In Colombia the most dangerous accidents are caused by Tityus pachyurus that is widely distributed around this country. In the Brazilian Amazonian region scorpion stings are a common event caused by Tityus obscurus. The main objective of this work was to perform the molecular cloning of the putative Na+-channel scorpion toxins (NaScTxs) from T. pachyurus and T. obscurus venom glands and to analyze their phylogenetic relationship with other known NaScTxs from Tityus species
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