Characterization of three "Birtoxin-like" toxins from the Androctonus amoreuxi scorpion venom

Comparative analyses and implications for antivenom serotherapy of four Moroccan scorpion Buthus occitanus venoms: Subspecies tunetanus, paris, malhommei, and mardochei

Temporary passive immunity such as serotherapy against venoms requires the full knowledge of all venom's components. Here, four venoms from Moroccan common yellow scorpions belonging to Buthus occitanus, subspecies tunetanus, paris, malhommei, and mardochei, all collected in four different restricted areas, were analysed in deep. They were fractionated by reversed-phase high-performance liquid chromatography (RP-HPLC) and their molecular masse profile determined by off-line MALDI-TOF mass spectrometry. Characterisation of their main components was achieved by enzyme-linked immunosorbent assay (ELISA) using specific antisera against the major lethal scorpion toxins identified so far, i.e. voltage-gated sodium channels (Na_v) modulators α- and β-toxins, as well as diverse potassium channel pore blocker toxins. For fractions with identical RP-HPLC retention times, we observe that their relative quantities show large differences. Moreover, identical masses present simultaneously in the four venoms are infrequent. ELISAs show that the majority of the RP-HPLC compounds cross-react with the antiserum against the "α-like" toxin Bot I, which has been previously identified in the Algerian Buthus occitanus tunetanus venom. Moreover, minor fractions were recognised by the antiserum against the highly lethal "classical" α-toxin of reference AaH II from the Androctonus australis venom. As such, our results bring new sights for further improving scorpion venom serotherapy in Morocco.

A first exploration of the venom of the Buthus occitanus scorpion found in southern France

Even though Buthus occitanus scorpions are found throughout the Mediterranean region, a lack of distinctive characteristics has hampered their classification into different subspecies. Yet, stings from this particular scorpion family are reported each year to result in pain followed by various toxic symptoms. In order to determine the toxicity origin of the rare French B. occitanus Amoreux scorpion, we collected several specimens and studied their venom composition using a nano ultra high performance liquid chromatography and matrix assisted laser desorption/ionisation time-of-flight mass spectrometry (nano UHPLC/MALDI-TOF-MS) automated workflow combined with an enzyme-linked immunosorbent assay (ELISA) approach. Moreover, we compared this dataset to that obtained from highly lethal Androctonus australis and Androctonus mauretanicus scorpions collected in North Africa. As a result, we found that the B. occitanus Amoreux venom is toxic to mice, an observation that is most likely caused by venom components that inhibit voltage-gated sodium channel inactivation. Moreover, we identified similarities in venom composition between B. occitanus scorpions living in the South of France and other Buthidae collected in Morocco and Algeria. As such, the results of this study should be taken into consideration when treating stings from the B. occitanus species living in the South of France.

Automatic determination of disulfide bridges in proteins

Precise determination of disulfide linkages between cysteine (Cys) residues in proteins is essential in the determination of protein structure. Therefore, a reliable automated method for the identification of disulfide bridges can serve as an important tool in the analysis of the tertiary structure of proteins of interest. Here, we describe the current and past methods used to identify disulfide bridges in proteins, with a focus on mass spectrometry (MS)-based methods and a particular emphasis on nanoliquid chromatography-tandem mass spectrometry (nanoLC-MS/MS)-based methods. We also show the development of an easy method based on the separation of disulfide-linked proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under denaturing and nonreducing conditions and selective in-gel digestion of proteins using reducing and nonreducing conditions, followed by analysis of the resulting peptide mixture by nanoACQUITY UPLC coupled to a quadrupole time-of-flight (QTOF) Micro mass spectrometer (nanoLC-MS/MS). Data-dependent analysis (DDA) nanoLC-MS/MS and information-dependent analysis (IDA) nanoLC-MS/MS were used for random and targeted identification of disulfide-linked peptides. Finally, an example of electrospray-MS (ESI-MS) and ESI-MS/MS-based determination of disulfide-linked peptides is shown.