Discovery of a novel antifungal agent: All-hydrocarbon stapling modification of peptide Aurein1.2

Systematic All-Hydrocarbon Stapling Analysis for Cecropin A Generates a Potent and Stable Antimicrobial Peptide

As an evolutionarily conserved family of antimicrobial peptides (AMPs), cecropins play an important role in innate immunity. But their inevitable weaknesses, including poor proteolytic stability and unpredictable cytotoxicity, severely hindered their clinical applications. Considering their two-helical structure, all-hydrocarbon stapling was performed on cecropin A, successfully generating 27 (i, i + 4) stapled derivatives. By evaluating antimicrobial and hemolytic activities, CEC-2-9 with the C-terminus threonine and lysine being stapled was identified as the optimal one. It exerted significantly enhanced antibacterial potency with more severe bacterial membrane damage capacity. Compared to cecropin A, its increased helicity and hydrophobicity as well as the decreased net charge also enabled its improved stability and biocompatibility, facilitating its enhanced antibacterial and anti-inflammatory efficacy for the effective treatment of mice with peritonitis sepsis. These results have proven that the systematic all-hydrocarbon stapling of AMPs was a feasible approach for the future development of antibacterial therapeutics.

Antimicrobial Peptides: Classification, Mechanism, and Application in Plant Disease Resistance

Antimicrobial peptides (AMPs) are a class of alkaline, small molecules found widely in nature. This article surveys the classifications of AMPs, delving into their modes of action and their role in controlling significant plant diseases caused by bacteria, viruses, and fungi. It also explores the prospects and challenges in this field, aiming to provide insights for enhancing crop disease resistance, ensuring food security, deepening the understanding of pathogen mechanisms, and protecting ecological balance.

All-hydrocarbon stapling enables improvement of antimicrobial activity and proteolytic stability of peptide Figainin 2

Figainin 2 is a cationic, hydrophobic, α-helical host-defense peptide with 28 residues, which was isolated from the skin secretions of the Chaco tree frog. It shows potent inhibitory activity against both Gram-negative and Gram-positive pathogens and has garnered considerable interest in developing novel classes of natural antibacterial agents. However, as a linear peptide, conformational flexibility and poor proteolytic stability hindered its development as antibacterial agent. To alleviate its susceptibility to proteolytic degradation and improve its antibacterial activity, a series of hydrocarbon-stable analogs of Figainin 2 were synthesized and evaluated for their secondary structure, protease stability, antimicrobial, and hemolytic activities. Among them, F2-12 showed significant improvement in protease resistance and antimicrobial activity compared to that of the template peptide. This study provides a promising strategy for the development of antimicrobial drugs.

Exploring biocompatible chemistry to create stapled and photoswitchable variants of the antimicrobial peptide aurein 1.2

Antibiotic resistance is an escalating global health threat. Due to their diverse mechanisms of action and evasion of traditional resistance mechanisms, peptides hold promise as future antibiotics. Their ability to disrupt bacterial membranes presents a potential strategy to combat drug-resistant infections and address the increasing need for effective antimicrobial treatments. Amphipathic α-helical peptides possess a distinctive molecular structure with both charged/hydrophilic and hydrophobic regions that interact with the bacterial cell membrane, disrupting its structural integrity. The α-helical amphipathic peptide aurein 1.2, secreted by the Australian frog Litoria aurea, is one of the shortest known antimicrobial peptides, spanning only 13 amino acids. The primary objective of this study was to investigate stapled and photoswitchable modifications of short helical peptides employing biocompatible chemistry, utilising aurein 1.2 as a model system. We developed various stapled versions of aurein 1.2 using biocompatible conjugation chemistry between dicyanopyridine and 1,2-aminothiols. While the commonly employed stapling pattern for longer staples is i, i + 7, we observed superior helicity in peptides stapled at positions i, i + 8. Molecular dynamics simulations confirmed both stapling patterns to support an α-helical peptide conformation. Additionally, we utilised a cysteine-selective photosensitive staple, perfluoro azobenzene, to explore photoswitchable variants of aurein 1.2. A double-cysteine variant stapled at i, i + 7 indeed exhibited a change in overall helicity induced by light. We further demonstrated the applicability of this staple to attach to cysteine residues in i, i + 7 positions of a helix in a model protein. While some of the stapled variants displayed substantial increase in helicity, minimal inhibitory concentration assays revealed that none of the stapled aurein 1.2 variants exhibited increased antimicrobial activity compared to the wildtype.