Structural Characterization of de Novo Designed L5K5W Model Peptide Isomers with Potent Antimicrobial and Varied Hemolytic Activities

Abstract

In an effort to develop short antimicrobial peptides with simple amino acid compositions, we generated a series of undecapeptide isomers having the L5K5W formula. Amino acid sequences were designed to be perfectly amphipathic when folded into a helical conformation by converging leucines onto one side and lysines onto the other side of the helical axis. The single tryptophans, whose positions were varied in the primary structures, were located commonly at the critical amphipathic interface in the helical wheel projection. Helical conformations and the tryptophanyl environments of the 11 L5K5W peptides were confirmed and characterized by circular dichroism, fluorescence and nuclear magnetic resonance spectroscopy. All of the isomers exhibited a potent, broad-spectrum of antibacterial activity with just a slight variance in individual potency, whereas their hemolytic activities against human erythrocytes were significantly diversified. Interestingly, helical dispositions and fluorescence blue shifts of the peptides in aqueous trifluoroethanol solutions, rather than in detergent micelles, showed a marked linear correlation with their hemolytic potency. These results demonstrate that our de novo design strategy for amphipathic helical model peptides is effective for developing novel antimicrobial peptides and their hemolytic activities can be estimated in correlation with structural parameters.

Strategies employed in the design and optimization of synthetic antimicrobial peptide amphiphiles with enhanced therapeutic potentials

“…It was found that a Val to Lys substitution in the center of the non-polar face of a 26-residue amphipathic α-helical AMP effectively reduced the overall hydrophobicity by disrupting the continuous hydrophobic surface into 2 regions and decreased peptide self-association in aqueous solution to permit a higher degree of association with the prokaryotic cell membranes. Other studies have also found that the appropriate positioning of Trp residue(s) at the hydrophobic-hydrophilic interface of the helical wheel projection could provide an effective strategy to enhance helical stability and also increase the partitioning or penetration of designed AMPs into microbial membrane lipid bilayers with minimal effects on mammalian cell membranes or their mimics at concentrations required for antimicrobial activities [56,58,59]. Although α-helical AMPs represent the most widely investigated class of AMPs, other types of secondary structures such as β-sheets [43,60] and β-hairpin-like AMPs [61,62] have also been designed and evaluated.…”

Latarcins: versatile spider venom peptides

“…The balance between antimicrobial and hemolytic effects has been discussed in numerous works [116,[140][141][142][143][144][145][146][147][148][149][150][151]. The hemolytic effect is especially pronounced for Ltc 2a (Table 4).…”

Anti-inflammatory action of an antimicrobial model peptide that suppresses the TRIF-dependent signaling pathway via inhibition of toll-like receptor 4 endocytosis in lipopolysaccharide-stimulated macrophages

“…Thus, we propose that our WALK11 peptides, which show both antimicrobial and anti-inflammatory activities, are promising molecules for the development of therapies for infectious inflammation. In addition, as suggested previously [8,9], the properties of these rationally designed WALK11 peptides (i.e., their short length and simple amino acid composition) could be regarded as favorable for reducing manufacturing costs and facilitating pharmaceutical optimization for pharmaceutical and/or industrial production of bioactive peptide agents. …”

“…In our previous work, WALK11 peptide isomers (refer to the amino acid sequences in Fig 1A) exhibited quite variable hemolytic activities against human erythrocytes, although their antimicrobial potencies were similar [8]. Thus, prior to investigating the anti-inflammatory potential of the peptides, we performed an MTT assay to assess their cytotoxicity against RAW264.7 macrophage cells.…”

“…The immunomodulatory properties of these AMPs are receiving a great deal of attention in studies aimed at developing new anti-inflammatory drugs [2]. In this context, we have recently developed a series of model peptide isomers, WALK11 peptides (tryptophan-containing, amphipathic-helical leucine/lysine undecapeptides) that share the same L 5 K 5 W formula and show potent antimicrobial activity [8,9] (Fig 1A). The aim of the present study was to investigate the anti-inflammatory potential of WALK11 peptides and to establish their mode of anti-inflammatory action.…”