Maurotoxin (MTX) is a 34-residue peptide from Scorpio maurus venom. It is reticulated by four disulfide bridges with a unique arrangement compared to other scorpion toxins that target potassium (K⁺) channels. Structure–activity relationship studies have not been well performed for this toxin family. The screening of Scorpio maurus venom was performed by different steps of fractionation, followed by the ELISA test, using MTX antibodies, to isolate an MTX-like peptide. In vitro, in vivo and computational studies were performed to study the structure–activity relationship of the new isolated peptide. We isolated a new peptide designated MTX1, structurally related to MTX. It demonstrated toxicity on mice eight times more effectively than MTX. MTX1 blocks the Kv1.2 and Kv1.3 channels, expressed in Xenopus oocytes, with IC₅₀ values of 0.26 and 180 nM, respectively. Moreover, MTX1 competitively interacts with both ¹²⁵I-apamin (IC₅₀ = 1.7 nM) and ¹²⁵I-charybdotoxin (IC₅₀ = 5 nM) for binding to rat brain synaptosomes. Despite its high sequence similarity (85%) to MTX, MTX1 exhibits a higher binding affinity towards the Kv1.2 and SKCa channels. Computational analysis highlights the significance of specific residues in the β-sheet region, particularly the R27, in enhancing the binding affinity of MTX1 towards the Kv1.2 and SKCa channels.

Scorpion venoms represent complex pharmacological arsenals whose complete molecular inventory remains incompletely defined, particularly for North African buthid species of high medical relevance. Buthus tunetanus is among the most clinically significant scorpion species across the Maghreb. We analysed the toxic fraction BotG50, isolated by Sephadex G-50 gel-filtration, using nanoLC-HRMS/MS coupled with an evidence-tiered, five-stage bioinformatics workflow. The workflow combines Proteome Discoverer database searching, BLAST-guided homology expansion, Casanovo de novo sequencing with variant construction, signal-peptide and propeptide removal, and post-translational modification (PTM) annotation. The analysis revealed 64 components (FDR < 1%), comprising 38 multi-peptide-supported identifications (≥2 peptides) and 26 single-peptide hits, with a median sequence coverage of 33%. The dominant neurotoxic repertoire includes toxins targeting K⁺, Na⁺, and Cl^- channels, α/β toxins, insect- or mammal-specific neurotoxins, and putative depressant toxins, while a minor accessory compartment comprises hyaluronidase, phospholipase A₂, lipolytic peptides, and hemocyanin-like proteins. BLAST analysis revealed strong sequence homologies with peptides from Buthus israelis (32.8%), B. tunetanus (15.6%), and Mesobuthus eupeus (10.9%). Approximately 52% of final identifications (33/64 proteins) required analytical stages beyond classical FASTA database searching. This proteomic atlas provides the most detailed molecular map of BotG50 to date, constituting a critical resource for antivenom epitope design, nanobody target selection, and bioactive peptide discovery.