Designing a Potent, Low-Toxicity Antimicrobial Peptide Inspired by Scorpion Peptides: Optimizing Expression and Activity.

Scorpion venom contains diverse antimicrobial peptides (AMPs) characterized by conserved structures across different species. The potency and small size of these AMPs have facilitated their production and application. However, natural AMPs often lack the necessary potency for clinical use due to instability and weak effect on a broad range of microbes, such as Gram-negative bacteria. To overcome the limited potency of scorpion AMPs, we designed Mu-17, a novel peptide based on a leucine zipper motif derived from the conserved structure of scorpion AMPs. Mu-17 consists of 17 residues, LFRLIPSLIKRLISAFK, that form an amphipathic alpha-helix structure. The gene encoding Mu-17 was constructed and cloned into a bacterial expression system. We optimized bacterial transformation and expression conditions to reduce the toxicity of Mu-17, a common challenge in the production of recombinant AMPs. The purified recombinant Mu-17 exhibited broad-spectrum antimicrobial activity against Gram-positive bacteria (Bacillus sp. and Staphylococcus sp.), Gram-negative bacteria (Escherichia coli), and the yeast Candida albicans, with minimum inhibitory concentrations (MICs) ranging from 1.5 to 5 µM. Additionally, Mu-17 inhibited breast cancer cell proliferation with an IC50 value of 13 µM. Mu-17 exhibited remarkably low hemolytic activity, at 18% for a 100 µM concentration, significantly improving over many potent AMPs with known toxicity issues. The antimicrobial activity of Mu-17 likely occurs through membrane interaction. Our findings demonstrate that bio-inspired design based on scorpion AMP leucine zipper-like motif can yield novel peptides with potent antimicrobial and anticancer activity along with reduced toxicity, positioning Mu-17 as a promising lead for therapeutic development.