Effects of Acyl versus Aminoacyl Conjugation on the Properties of Antimicrobial Peptides

Abstract

To investigate the importance of increased hydrophobicity at the amino end of antimicrobial peptides, a dermaseptin derivative was used as a template for a systematic acylation study. Through a gradual increase of the acyl moiety chain length, hydrophobicity was monitored and further modulated by acyl conversion to aminoacyl. The chain lengths of the acyl derivatives correlated with a gradual increase in the peptide's global hydrophobicity and stabilization of its helical structure. The effect on cytolytic properties, however, fluctuated for different cells. Whereas acylation gradually enhanced hemolysis of human red blood cells and antiprotozoan activity against Leishmania major, bacteria displayed a more complex behavior. The gram-positive organism Staphylococcus aureus was most sensitive to intermediate acyl chains, while longer acyls gradually led to a total loss of activity. All acyl derivatives were detrimental to activity against Escherichia coli, namely, but not solely, because of peptide aggregation. Although aminoacyl derivatives behaved essentially similarly to the nonaminated acyls, they displayed reduced hydrophobicity, and consequently, the long-chain acyls enhanced activity against all microorganisms (e.g., by up to 12-fold for the aminolauryl derivative) but were significantly less hemolytic than their acyl counterparts. Acylation also enhanced bactericidal kinetics and peptide resistance to plasma proteases. The similarities and differences upon acylation of MSI-78 and LL37 are presented and discussed. Overall, the data suggest an approach that can be used to enhance the potencies of acylated short antimicrobial peptides by preventing hydrophobic interactions that lead to self-assembly in solution and, thus, to inefficacy against cell wall-containing target cells.Peptide-based antimicrobials represent a promising class of novel antimicrobial agents (2,24,30,60). A large body of data indicates that antimicrobial peptides kill target cells by destabilizing the structure of cell membranes by a mechanism whose fine details remain to be fully understood (18,25,45). Antimicrobial peptides also display a variety of interesting properties: they may activate the microbicidal activities of leukocytes and monocytes/macrophages (1,46,47), suppress the production of inflammatory cytokines, offer protection from the cascade of events that lead to endotoxic shock (10,16,29), and display synergistic activity in the presence of other peptides (26,35,57) or conventional antibiotics (22). Antimicrobial peptide genes introduced into the genomes of plants endowed the plants with resistance to pathogens (40). These multifunctional peptides may be useful in food preservation (9, 58), as imaging probes for the detection of bacterial or fungal infection loci (56), and as linings for medical and surgical devices (4, 23). Clearly, the externally localized site of action and receptor-independent mechanism of peptide-based antimicrobials may significantly prevent drug resistance. However, this mechanism is also largely resp...

Antibacterial Properties of Dermaseptin S4 Derivatives under Extreme Incubation Conditions

“…As shown in Table 1, the highly hydrophobic native dermaseptin S4 was unable to reach an MIC at the highest concentration tested (MIC, Ͼ32 M), very likely because of its inability to effectively cross the external membrane and reach the cytoplasmic membrane due to its high level of self-assembly in solution (critical micelle concentration ϭ 0.2 M), as reported previously (44). Therefore, with increasing charge, hydrophobicity was reduced, aggregation was limited, and activity was enhanced (MIC of P 28 , 8 M).…”

“…N acylation was recently shown to stabilize structure and improve antimicrobial properties of short dermaseptin derivatives (44) and other AMPs (3,4,9,10,33,34,49). As shown in Table 1, C12-P 14 was unable to reach an MIC at the highest concentration tested (MIC, Ͼ32 M), very likely because of its high level of self-assembly in solution on May 9, 2018 by guest http://aac.asm.org/ (reminiscent of native dermaseptin S4).…”

“…AMPs from the dermaseptin family were recently proposed as model peptides for investigating the effects of acyl conjugation (13,17,44). These amphibian-derived AMPs (35, 36) have been amply investigated during the past decade and shown to exert rapid cytolytic activity against a wide range of microorganisms, including gram-negative and gram-positive bacteria, protozoa, filamentous fungi (14,26,35,36), spores of pathogenic bacteria (29), yeasts (11), and intracellular parasites (13,17,30), as well as antiviral activity (5).…”

Bacterial Capture by Peptide-Mimetic Oligoacyllysine Surfaces

“…(28). Statistical data for each experiment were obtained from at least two independent assays performed in duplicate.…”

Antibacterial Properties of an Oligo-Acyl-Lysyl Hexamer Targeting Gram-Negative Species

“…The sequence specificity of these activities was provided by a closely related derivative (C 12 K-5␣ 10 ), demonstrating that when the N-terminal amino group was removed, the resulting sequence was nearly devoid of activity against most bacteria (i.e., MICs Ͼ 90 g/ml; data not shown) and was cytotoxic to both erythrocytes and HFFs (Fig. 2), as is often observed with excessively hydrophobic OAKs (13) and HDPs (15,26). Indeed, C 12 K-5␣ 10 displayed a higher elution time in HPLC than ␣ 12 -5␣ 10 (50.2 versus 41.5 min) and lower solubility in PBS (critical aggregation concentration, 18 versus Ͼ180 g/ml).…”