Cathelicidin-derived Trp/Pro-rich antimicrobial peptides with lysine peptoid residue (Nlys): therapeutic index and plausible mode of action.
Recently, we designed a novel cell-selective antimicrobial peptide (TPk) with intracellular mode of action from Pro --> Nlys (Lys peptoid residue) substitution in a noncell-selective cathelicidin-derived Trp/Pro-rich antimicrobial peptide, tritrpticin-amide (TP; VRRFPWWWPFLRR-NH(2)) (Biochemistry 2006; 45: 13007-13017). In this study, to elucidate the effect of Pro --> Nlys substitution on therapeutic index and mode of action of other noncell-selective cathelicidin-derived Trp/Pro-rich antimicrobial peptides and develop novel short antimicrobial peptides with high cell selectivity/therapeutic index, we synthesized Nlys-substituted antimicrobial peptides, TPk, STPk and INk, in which all proline residues of TP, symmetric TP-analogue (STP; KKFPWWWPFKK-NH(2)) and indolicidin (IN; ILPWKWPWWPWRR-NH(2)) were replaced by Nlys, respectively. Compared to parent Pro-containing peptides (TP, STP and IN), Nlys substituted peptides (TPk, STPk and Ink) had 4- to 26-fold higher cell selectivity/therapeutic index. Parent Pro-containing peptides induced a significant depolarization of the cytoplasmic membrane of intact Staphylococcus aureus at their MIC, whereas Nlys-substituted antimicrobial peptides did not cause visible membrane depolarization at their MIC. These results suggest that the antibacterial action of Nlys-substituted peptides is probably not due to the disruption of bacterial cytoplasmic membranes but the inhibition of intracellular components. Taken together, our results showed that Pro --> Nlys substitution in other noncell-selective Trp/Pro-rich antimicrobial peptides such as STP and IN as well as TP can improve the cell selectivity/therapeutic index and change the mode of antibacterial action from membrane-disrupting to intracellular targeting. In conclusion, our findings suggested that Pro --> Nlys substitution in noncell-selective Trp/Pro-rich antimicrobial peptides is a promising method to develop cell-selective antimicrobial peptides with intracellular target mechanism.
Zhu
Wan Long
WL
Department of Bio-Materials, Graduate School and Research Center for Proteineous Materials, Chosun University, Gwangju 501-759, Korea.
Hahm
Kyung-Soo
KS
Shin
Song Yub
SY
D000900:Anti-Bacterial Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D001419:Bacteria / Q000254:growth & development* / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism; D006461:Hemolysis / Q000187:drug effects; D053878:Hemolytic Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D034444:Peptoids / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D054804:Cathelicidins
D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D053878:Hemolytic Agents; D034444:Peptoids; D054804:Cathelicidins