Rational Design of α-Helical Antimicrobial Peptides with Enhanced Activities and Specificity/Therapeutic Index

Abstract

In the present study, the 26-residue peptide sequence Ac-KWKSFLKTFKSAVKTVLHTALKAISS-amide (V 681 ) was utilized as the framework to study the effects of peptide hydrophobicity/hydrophilicity, amphipathicity, and helicity (induced by single amino acid substitutions in the center of the polar and nonpolar faces of the amphipathic helix) on biological activities. The peptide analogs were also studied by temperature profiling in reversed-phase high performance liquid chromatography, from 5 to 80°C, to evaluate the self-associating ability of the molecules in solution, another important parameter in understanding peptide antimicrobial and hemolytic activities. A higher ability to self-associate in solution was correlated with weaker antimicrobial activity and stronger hemolytic activity of the peptides. Biological studies showed that strong hemolytic activity of the peptides generally correlated with high hydrophobicity, high amphipathicity, and high helicity. In most cases, the D-amino acid substituted peptides possessed an enhanced average antimicrobial activity compared with L-diastereomers. The therapeutic index of V 681 was improved 90-and 23-fold against Gram-negative and Gram-positive bacteria, respectively. By simply replacing the central hydrophobic or hydrophilic amino acid residue on the nonpolar or the polar face of these amphipathic derivatives of V 681 with a series of selected D-/L-amino acids, we demonstrated that this method has excellent potential for the rational design of antimicrobial peptides with enhanced activities.

Alpha-helical cationic antimicrobial peptides: relationships of structure and function

“…The clinical potential of a given AMP is assessed by the ratio of MHC and MIC, or therapeutic index. Therapeutic index (MHC/MIC) can be improved by increasing the antimicrobial activity, decreasing hemolytic activity or both (Chen et al, 2005). High therapeutic index indicates low cytotoxic activity (high MHC value) but high antimicrobial activity (low MIC value).…”

“…Previous studies have shown that peptide self-association (i. e., the ability to dimerize) in aqueous solutions is a important parameter for antimicrobial activity (Chen et al, 2005). If the self-association ability of a peptide is too strong in aqueous medium, it could decrease the ability of the peptide to dissociate, to pass through the capsule and cell wall of microorganisms, and to penetrate into the cytoplasmic membrane to kill target cells.…”

“…(Chen et al, 2005). V 681 peptide has strong hemolytic activity and high antimicrobial activity against Gram-negative and Gram-positive bacteria (Zhang et al, 1998;Zhang et al, 1999).…”

Membrane interactions of designed cationic antimicrobial peptides: The two thresholds

“…39 The peptide retention times (R t values) are shown in Table III. As expected, the tetra-substituted Ala-to-Leu peptide 6K-F17-4L 8,11,13,16 was retained the longest on the HPLC column among the Ala-substituted series, followed by triple, double, hairpin (SPGS-34), mono-Leu, cyclic, and nonsubstituted peptides, followed finally the least hydrophobic Ala-to-Asp substituted-7K-F18-1D 17 .…”

Antitumor activity of a membrane lytic peptide cyclized with a linker sensitive to membrane type 1-matrix metalloproteinase

“…Due to the growing drug resistance against conventional antibiotics, these peptides have become candidates of a new class of antibiotics (3,4). More recently, their potential as novel anticancer reagents has been explored (5 -7).…”