Molecular Insights into the Mode of Action of Antibacterial Peptides Derived from Chicken Plasma Hydrolysates

Due to the overuse and abuse of antibiotics, several antibiotic resistant bacteria have emerged. Antimicrobial peptides (AMPs) have gained attention as alternative antimicrobial agents because of their unique mode of action that impedes bacterial resistance. Two novel antibacterial peptides were isolated from Alcalase-hydrolyzed chicken plasma by size exclusion and reverse-phase chromatography. They were identified by LC-MS/MS to be VSDH and CCCPKAF, which showed effective antibacterial activity toward Bacillus cereus DMST 5040, with varied modes of action. The peptide CCCPKAF caused cell membrane disintegration, as evidenced by propidium iodide (PI) uptake. In contrast, the peptide VSDH targeted intracellular molecules, including proteins and nucleic acids, as revealed by Synchrotron-based Fourier Transform Infrared (SR-FTIR). The secondary structure of intracellular proteins increased to a beta-sheet structure concomitant with a decrease in the alpha-helix structure when exposed to 0.5 mM VSDH. Molecular docking analysis revealed that VSDH showed high binding affinity for the active sites of the various enzymes involved in DNA synthesis. In addition, it showed good affinity for a chaperone protein (Dnak), resulting in the misfolding of intracellular proteins. Nuclear magnetic resonance (NMR) and molecular dynamics simulations also indicated that VSDH chelated well with Mg2+, which could partly contribute to its antibacterial activity.

Automated summary

Due to the overuse and abuse of antibiotics, antibiotic resistant bacteria have emerged. Antimicrobial peptides (AMPs) are gaining attention as alternative antimicrobial agents due to their unique mode of action that hinders bacterial resistance. This study isolated and identified two novel antibacterial peptides, VSDH and CCCPKAF, from Alcalase-hydrolyzed chicken plasma, which showed effective antibacterial activity against Bacillus cereus DMST 5040 with different mechanisms of action. VSDH targeted intracellular molecules, while CCCPKAF caused cell membrane disintegration. Molecular docking analysis revealed that VSDH had high binding affinity for enzymes involved in DNA synthesis and a chaperone protein, leading to the misfolding of intracellular proteins. NMR and molecular dynamics simulations suggested that VSDH chelated with Mg2+, contributing to its antibacterial activity.