Identification and synthesis of a long‐chain antimicrobial peptide from the venom of the <i>Liocheles australasiae</i> scorpion

Scorpion venom contains linear peptides without disulfide bonds in addition to peptides with disulfide bonds. Many such linear peptides have an amphiphilic α-helical structure, often with antimicrobial activity and can be classified into three groups based on their molecular size. Among them, long-chain antimicrobial peptides consisting of more than 40 residues have not been thoroughly studied due to the difficulty of synthesizing them. We have previously reported a transcriptome analysis of the venom gland of Liocheles australasiae that revealed precursor sequences of long-chain antimicrobial peptides. In the study reported here, we identified the mature structure of one such long-chain antimicrobial peptide, LaCT1, which we synthesized using chemical ligation to confirm its structure and evaluate its biological activities. The result showed that LaCT1 exhibited significant antimicrobial activity. In addition, we identified its partial peptides consisting of an N- or C-terminal region, which may be generated by enzymatic cleavage in the venom. Among them, only the peptide containing the N-terminal half region was active. LaCT1 also not only showed insecticidal activity but also synergistically enhanced the effects of another insecticidal peptide identified in L. australasiae venom as well. These results provide insights into the role of antimicrobial peptides in scorpion venom.