Rational Design of Helix‐Stabilized Antimicrobial Peptide Foldamers Containing α,α‐Disubstituted Amino Acids or Side‐Chain Stapling

Abstract

Antimicrobial peptides (AMPs) are expected to be good candidate molecules for novel antimicrobial therapies. Most AMPs exert their antimicrobial activity through disruption of microbial membranes due to their amphipathic properties. Recently, the helical peptide ‘Stripe’ was reported by our group, a rationally designed amphipathic AMP focused on distribution of natural cationic and hydrophobic amino acid residues. In this study, a set of Stripe‐based AMP foldamers was designed, synthesized and investigated that contain α,α‐disubstituted amino acids or side‐chain stapling to stabilize their helical structures. Our results showed that a peptide containing 2‐aminoisobutyric acid (Aib) residues exhibited potent antimicrobial activity against both Gram‐positive S.aureus (MIC value: 3.125 μM) and Gram‐negative bacteria (including a multidrug‐resistant strain, MDRP, MIC value: 1.56 μM), without significant hemolytic activity (>100 μM). Electrophysiological measurements revealed that this peptide formed stable pores in a 1,2‐dioleoyl‐sn‐glycero‐3‐phosphoethanolamine (DOPE)/1,2‐dioleoyl‐sn‐glycero‐3‐phosphoglycerol (DOPG) bilayer but not in a dioleoylphosphocholine (DOPC) bilayer. The introduction of Aib residues into Stripe could be a promising way to increase the antimicrobial activity of AMP foldamers, and the peptide could represent a promising novel therapeutic candidate to treat multidrug‐resistant bacterial infection.

Structure–activity relationship study of amphipathic antimicrobial peptides using helix‐destabilizing sarcosine

“…Thus, replacement of glycine, alanine and leucine residues with sarcosine disrupted the α-helical structure of Stripe. Comparing with Stripe 2 and a Stripe analogue in which alanine was replaced with glycine in our previous study, 13 the helicity of Stripe 2 was lower than that of the analogue, which suggested the destabilization effect of sarcosine is stronger than that of glycine.…”

“…Antimicrobial peptides targeting microbial membranes can be cytotoxic, and their toxicity is often unrelated to their antimicrobial activity. 13 Therefore, the toxicity of Stripe 1-5 was examined.…”

The effects of magainin 2-derived and rationally designed antimicrobial peptides on Mycoplasma pneumoniae

“…pneumoniae . PI uptake assays showed that 17base-Ac 6 c, 17base-Hybrid, Block, and NK2A have membrane disruption activities, indicating the cationic moiety at the terminal of AMPs as well as alpha-helical structure stability is important for membrane disruption activity; however, based on the PI uptake assay results and previous reports [ 11 – 13 ], although the higher membrane disruption activity basically relates to the anti-Mp effect, the AMP sequences would also affect, indicating the intracellular targets. In summary, the AMP features with terminal cationic moiety and stabilised alpha-helical structure could be potent novel antimicrobials for M .…”

“…All the AMPs used in this study have been reported to have antimicrobial effects [ 11 – 13 ]. Mag2 is least effective against S .…”

“…The purity of peptides was assessed using analytical HPLC and a Discovery ® BIO Wide Pore C18 column (25 cm × 4.6 mm; solvent A: 0.1% TFA/water, solvent B: 0.1% TFA/acetonitrile, flow rate: 1.0 mL/min, gradient: 10%–100% gradient of solvent B over 30 min). Block, Stripe, and Random were synthesised as previously reported [ 12 , 13 ]. NK2A was synthesised as previously reported [ 19 ].…”