In silico and in vitro characterization of VC15, a short peptide derived from Pin2

Antimicrobial peptides (AMPs) are promising alternatives to conventional antibiotics, although their clinical application is often limited by cytotoxicity and poor selectivity. Here, we investigated the mechanism of action and biological activity of VC15, a short peptide derived from Pin2, combining molecular dynamics simulations with experimental assays. Simulations in bacterial (POPC:POPG) and mammalian (POPC:cholesterol) membrane models revealed that both peptides predominantly adopt a surface-bound state. Aromatic residues, particularly phenylalanine and tryptophan, play a central role in membrane anchoring. In bacterial membranes, both peptides preferentially adopt horizontal orientations and interact strongly with anionic lipids, promoting local membrane perturbation. In contrast, VC15 shows reduced penetration depth, fewer hydrophobic contacts, and lower membrane deformation compared to Pin2, especially in mammalian membranes. Consistently, liposome leakage assays showed that VC15 exhibits lower membrane-disruptive activity (EC₅₀ > 8 μM) than Pin2 (0.035 μM). VC15 displayed selective antibacterial activity against Streptococcus agalactiae (MIC = 6.25 μM), but reduced activity against Escherichia coli (MIC >50 μM), whereas Pin2 showed similar activity against both strains (MIC = 12.5 μM). Additionally, VC15 exhibited reduced hemolytic activity and lower cytotoxicity in keratinocyte and fibroblast cell lines. Overall, VC15 retains antibacterial activity while minimizing membrane disruption in mammalian systems, highlighting its potential as a selective antimicrobial candidate with an improved safety profile.