Antimicrobial Activity of Snake β-Defensins and Derived Peptides

beta-defensins are antimicrobial peptides presenting in vertebrate animals. They participate in innate immunity, but little is known about them in reptiles, including snakes. Although several beta-defensin genes were described in Brazilian snakes, their function is still unknown. The peptide sequence from these genes was deduced, and synthetic peptides (with approximately 40 amino acids and derived peptides) were tested against pathogenic bacteria and fungi using microbroth dilution assays. The linear peptides, derived from beta-defensins, were designed applying the bioisosterism strategy. The linear beta-defensins were more active against Escherichia coli, Micrococcus luteus, Citrobacter freundii, and Staphylococcus aureus. The derived peptides (7-14 mer) showed antibacterial activity against those bacteria and on Klebsiella pneumoniae. Nonetheless, they did not present activity against Candida albicans, Cryptococcus neoformans, Trychophyton rubrum, and Aspergillus fumigatus showing that the cysteine substitution to serine is deleterious to antifungal properties. Tryptophan residue showed to be necessary to improve antibacterial activity. Even though the studied snake beta-defensins do not have high antimicrobial activity, they proved to be attractive as template molecules for the development of antibiotics.

Automated summary

This study discovered beta-defensin genes in Brazilian snakes and tested the antimicrobial and antifungal activity of their synthetic peptides. The results showed that these beta-defensins have moderate antibacterial activity against certain bacteria, but weak antifungal properties. Additionally, the presence of tryptophan residue is necessary for improved antibacterial activity. The study concludes that snake beta-defensins could be potential template molecules for antibiotic development.