A Novel Linear Amphipathic β-Sheet Cationic Antimicrobial Peptide with Enhanced Selectivity for Bacterial Lipids

Abstract

All known naturally occurring linear cationic peptides adopt an amphipathic ␣-helical conformation upon binding to lipids as an initial step in the induction of cell leakage. We designed an 18-residue peptide, (KIGAKI) 3 -NH 2 , that has no amphipathic character as an ␣-helix but can form a highly amphipathic ␤-sheet. When bound to lipids, (KIGAKI) 3 -NH 2 did indeed form a ␤-sheet structure as evidenced by Fourier transform infrared and circular dichroism spectroscopy. The antimicrobial activity of this peptide was compared with that of (KI-AGKIA) 3 -NH 2 , and it was better than that of GMASKA-GAIAGKIAKVALKAL-NH 2 (PGLa) and (KLAGLAK) 3 -NH 2 , all of which form amphipathic ␣-helices when bound to membranes. (KIGAKI) 3 -NH 2 was much less effective at inducing leakage in lipid vesicles composed of mixtures of the acidic lipid, phosphatidylglycerol, and the neutral lipid, phosphatidylcholine, as compared with the other peptides. However, when phosphatidylethanolamine replaced phosphatidylcholine, the lytic potency of PGLa and the ␣-helical model peptides was reduced, whereas that of (KIGAKI) 3 -NH 2 was improved. Fluorescence experiments using analogs containing a single tryptophan residue showed significant differences between (KIGAKI) 3 -NH 2 and the ␣-helical peptides in their interactions with lipid vesicles. Because the data suggest enhanced selectivity between bacterial and mammalian lipids, linear amphipathic ␤-sheet peptides such as (KIGAKI) 3 -NH 2 warrant further investigation as potential antimicrobial agents.

Rational combinatorial design of pore-forming β-sheet peptides

“…This idea is supported by our observation that all peptides tested that conform to the active motif have comparable poreforming activity. Similarly, other authors have shown that antimicrobial activity of pore-forming peptides can be surprisingly insensitive to alterations in sequence, length, or even secondary structure (21,22). New libraries need to be screened with framework sequences based on the pore-forming motif identified in this work.…”

Interaction and Lipid-Induced Conformation of Two Cecropin−Melittin Hybrid Peptides Depend on Peptide and Membrane Composition

“…Although CD spectra recorded in the presence of lipid systems only provide a weighed average of the membrane-bound and free peptide conformations, both conventional CD and oriented circular dichroism (OCD) have been proven useful for the analysis of peptide conformational changes upon interaction with model membranes. 27,31,32,41,42 We herein report the study of the interactions between the antimicrobial peptides CA(1-8)M(1-18) and CA(1-7)M(2-9) and large unilamellar vesicles (LUVs) of three different lipid bilayer systems: zwitterionic DMPC, anionic DMPG, and a DMPC/DMPG 3:1 mixture. The study was carried out by DSC, QELS, and CD, so that the effect of the peptides on vesicle thermotropic phase behavior (DSC), charge, and size (QELS) could be related to membrane-induced changes in peptide structure (CD).…”

NMR methods for studying membrane‐active antimicrobial peptides

“…In many cases, it is known that a low concentration of peptides does not exert any antimicrobial effect, below a threshold concentration. For PGLa and similar model peptides, about 1 peptide per 30 lipids was needed to get an atnimicrobial effect (32). It would, thus, be interesting to vary the peptide/lipid molar ratio (P/L) and study the peptide-peptide interactions emerging at higher peptide concentrations, but this is not easily done in micelles.…”