Molecular Cloning and Functional Identification of the Antimicrobial Peptide Gene Ctri9594 from the Venom of the Scorpion Chaerilus tricostatus

Scorpion venom is a mixture of bioactive peptides, among which neurotoxins and antimicrobial peptides serve especially vital functions. Scorpion venom peptides in Buthidae species have been well described, but toxic peptides from non-Buthidae species have been under-investigated. Here, an antimicrobial peptide gene, Ctri9594, was cloned and functionally identified from the venom of the scorpion Chaerilus tricostatus. The precursor nucleotide sequence of Ctri9594 is 199 nt in length, including a 43 nt 5 ' UTR, 115 nt 3 ' UTR and 210 nt ORF. The ORF encodes 69 amino acid residues, containing a 21 aa signal peptide, 14 aa mature peptide, 3 aa C-terminal posttranslational processing signal and 31 aa propeptide. Multiple sequence alignment and evolutionary analyses show that Ctri9594 is an antimicrobial peptide in scorpion venom. The mature peptide of Ctri9594 was chemically synthesized with a purity greater than 95% and a molecular mass of 1484.4 Da. Minimum inhibitory concentrations (MICs) indicate that the synthesized mature peptide of Ctri9594 has inhibitory activity against Gram-positive bacteria (Bacillus thuringensis, Bacillus subtilis, Staphylococcus aureus and Micrococcus luteus) but not Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) or a fungus (Candida albicans). The antimicrobial mechanism of Ctri9594 is inferred to be related to its amphiphilic alpha-helix structure.