Abstract

Many scorpion accidents occur in the Brazilian Amazonian region and are frequently caused by Tityus obscurus. Approximately 5% of the crude venom of this species is composed of short linear, non-disulfide-bridged peptides, which have not been intensively investigated. As a consequence, only a few of these peptides have been structurally and functionally characterized to date. In the present paper, the peptide fraction of the venom was subjected to peptide profiling using an LCMS-IT-TOF/MS and MSn system. The analysis detected 320 non-disulfide bond-containing peptides (NDBPs), of which twenty-seven had their sequences assigned; among them, thirteen peptides were characterized, constituting novel toxins in T. obscurus venom. Some of the novel peptides showed similarities to hypotensin-like toxins, while other peptides appear to be natural fragments of neurotoxins. The novel peptides were submitted to a series of bioassays, revealing that many are multifunctional toxins that cause, for example, pain, edema formation and hemolysis to potentiate strong inflammatory processes and alterations in the locomotion and lifting activities in the victims of stinging. Knowledge of the complex matrix of peptides composing the venom of T. obscurus will contribute to better understanding of the complex mechanism of envenoming caused by stinging accidents. Significance: The scorpion Tityus obscurus causes many envenoming accidents of medical importance in Brazilian Amazon region; despite to this, very few is known about the toxinology of this animal. The knowledge about the venom composition and mechanisms of action is very important to understand the physiopathology processes related to the envenoming caused by this animal. The proteopeptidomic investigations of scorpion venoms in general have focused mainly the neurotoxins (which are disulfide bonds containing peptides) and large proteins. The short, linear, non-disulfide bonds containing peptides (NDBPs) represent up to 5% of scorpion venom compositions; however, they have been few investigated in comparison with the neurotoxins. The present study used a mass spectrometric approach to detect 320 NDBPs and to sequence 27 of them; pharmacological assays permitted to characterize 13 NDBPs as novel toxins involved with inflammation, pain and edema formation.