Improved antimicrobial activity of h‐lysozyme (107–115) by rational Ala substitution

Abstract

The most challenging target in the design of new antimicrobial agents is the development of antibiotic resistance. Antimicrobial peptides are good candidates as lead compounds for the development of novel anti-infective drugs. Here we propose the sequential substitution of each Ala residue present in a lead peptide with known antimicrobial activity by specific amino acids, rationally chosen, that could enhance the activity of the resultant peptide. Taking the fragment 107-115 of the human lysozyme as lead, two-round screening by sequentially replacing both Ala residues (108 and 111) by distinct amino acids resulted in a novel peptide with 4- and 20-fold increased antimicrobial activity against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213, respectively. These results reinforce the strategy proposed, which, in combination with simple and easy screening tools, will contribute to the rapid development of new therapeutic peptides required by the market.

Structural glance into a novel anti‐staphylococcal peptide

“…All residues except Tyr are present in peptide [K 108 W 111 ] 107‐115 hLz. Furthermore, Lys and Trp match the Ala‐substitutions in positions 108 and 111, derived from our screening (shown in red) . This finding suggests that this combination confers the resultant peptide the capacity to target and bind to anionic interfaces, such as micelles and microbial plasma membranes, thereby resulting in enhanced anti‐staphylococcal activity, as assessed in our previous work …”

“…Correspondingly, the MIC value was 4‐fold lower. For this peptide, the positive charge of Lys 108 played a major role for the enhanced anti‐staphylococcal activity and for determining its specificity for negative over zwitterionic membranes, like those of erythrocytes, as demonstrated by its lower hemolytic activity . The increase in the overall positive charge of peptides might enhance their affinity for negative membranes .…”

“…Those authors concluded that Trp, Trp, and Arg are key residues for the interaction with SDS micelles. Additionally, residues Lys, Tyr, Trp, Trp, and Arg present the highest chemical shift deviations upon binding to SDS micelles, thus supporting the notion of their key role in micelle‐binding. All residues except Tyr are present in peptide [K 108 W 111 ] 107‐115 hLz.…”

“…In our previous work, we introduced a new peptide derived from the 107–115 human lysozyme fragment (107‐115 hLz) exhibiting a 4‐ and 20‐fold increase in antimicrobial activity against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213, respectively . This fragment was selected from the helical hairpin domain of the human lysozyme because it showed stronger bactericidal activity than other fragments and the entire enzyme against a repertoire of microorganisms .…”

“…Peptide safety was assessed by hemolytic activity, resulting significant at 10‐fold its minimal anti‐staphylococcal concentration. This new peptide was called [K 108 W 111 ] 107‐115 hLz and was selected in a two‐round screening from 16 analogs substituted at positions 108 and 111 as described previously . All positively charged and hydrophobic amino acids were included in the screening as antimicrobial‐linked amino acids, because of their potential contribution to the amphiphilic balance of the resultant peptides; a feature proposed to be responsible for peptide interaction with microbial membranes .…”