Rational design of hyperstable antibacterial peptides for food preservation

Website Link (Journal by Vishweshwaraiah et. al.)

Abstract

We describe the design of peptides with properties like thermostability, pH stability, and antibacterial activity against a few bacterial food pathogens. Insights obtained from classical structure-function analysis of natural peptides and their mutants through antimicrobial and enzymatic assays are used to rationally develop a set of peptides. pH and thermostability assays were performed to demonstrate robust antimicrobial activity post-treatment with high temperatures and at wide pH ranges.

We have also investigated the mode of action of these hyperstable peptides using membrane permeability assays, electron microscopy, and molecular dynamics simulations.

Notably, through mutational studies, we show that these peptides elicit their antibacterial action via both membrane destabilization and inhibition of intracellular trypsin—the two functions attributable to separate peptide segments.

Finally, toxicity studies and food preservation assays demonstrate the safety and efficacy of the designed peptides for food preservation.

Overall, the study provides a general ‘blueprint’ for the development of stable antimicrobial peptides (AMPs). Insights obtained from this work may also be combined with combinatorial methods in high-throughput studies for future development of antimicrobials for various applications.

Content

In this study, we attempt to design possible alternatives to antimicrobial peptides like Nisin. We ‘rationally’ develop new peptides that simultaneously possess multiple properties like stability at a broad range of pH, thermostability, and anti-trypsin activity. Bowman–Birk inhibitors (BBIs) are a class of serine protease inhibitors that are highly stable28.

These contain a conserved nine-residue loop responsible for protease inhibitory activity. Various BBIs are already being used to contain insect growth29 and for therapeutic applications28,30,31,32,33,34,35.

Based on our analysis of the structure and activity of this peptide class, our design strategy involves recognizing and incorporating multiple ‘desirable properties’ to obtain robust antibacterial agents with high stability. Preliminary studies suggest that these peptides are safe and could in principle be employed to increase the shelf life of food products. We also attempt to decipher their mode of action.

Molecular dynamics (MD) simulation studies on the peptide-membrane complex shed light on the underlying peptide-membrane interactions that result in the antimicrobial action.

Overall, this study provides insights into the mechanism of action of such class of peptides and demonstrates how multiple properties can be rationally incorporated to develop superior antibacterial peptides. Most importantly, some of these insights are broadly applicable to the design of antimicrobials for clinical and biomedical applications, in addition to food preservation.