Molecular identification of peptide toxin MeBTX from venom glands of scorpion (Mesobuthus eupeus) in Iran

Considering the lack of knowledge of the molecular biology of scorpion venom antibacterial peptides، as a first step we sequenced and identified a full-length sequence from the venom glands of scorpion (Mesobuthus eupeus) through RT-PCR. Scorpion toxin consists of different types of toxins and enzymes which are encoded by individual genes. Antimicrobial peptides are cytolytic peptides that can rapidly kill a broad range of microbes and have additional activities that impact on the quality and effectiveness of innate responses and inflammation. These peptides had been found from a wide variety of organisms in the last few years. Scorpions were provided and identified by Razi Institute in Ahvaz. The origin of the total RNA was the telson، the last segment of the tail containing the two venom glands. Using RNX plus solution (CinnaGen، Iran)، the total RNA was extracted according to the manufacturer’s instructions. Then، cDNA was synthesized with the extracted total RNA as template and oligo (dT) as primer. In order to amplify cDNA encoding neurotoxin، RT-PCR was performed. The amplified cDNA fragments were sequenced in both strands according to the dideoxy termination method. Sequence comparisons with GenBank database were done using the BLAST software. Based on the sequence data، the complete sequence contained 273 nucleotides called MeBTXA signal peptide sequence was identified، and the glycine at position 20 was assumed to represent the start of the mature protein. Remarkably، they share 96، 94 and 67% similarity with the long-chain potassium ion channel blocker from Mesobuthus martensii، Buthus occitanus Israelis and Tityus costatus. Domain analysis of the protein showed «Arthropod defensin» between amino acid resides 55 to 85. This domain which is rich in cysteine is belongs to the antibacterial peptide family and has effect on the gram positive bacteria. This high sequence similarity together with completely conserved in the positions of all 6 cysteine indicated that this gene is a new member of β-toxin from the Iranian M. eupeus which may originate from a common ancestor.