Peptides with the Same Composition, Hydrophobicity, and Hydrophobic Moment Bind to Phospholipid Bilayers with Different Affinities

Abstract

We investigated the dependence of membrane binding on amino acid sequence for a series of amphipathic peptides derived from δ-lysin. δ-Lysin is a 26 amino acid, N-terminally formylated, hemolytic peptide that forms an amphipathic α-helix bound at membrane–water interfaces. A shortened peptide, lysette, was derived from δ-lysin by deletion of the four N-terminal amino acid residues. Five variants of lysette were synthesized by altering the amino acid sequence such that the overall hydrophobic moment remained essentially the same for all peptides. Peptide–lipid equilibrium dissociation constants and helicities of peptides bound to zwitterionic lipid vesicles were determined by stopped-flow fluorescence and circular dichroism. We found that binding to phosphatidylcholine bilayers was a function of the helicity of the bound peptide alone and independent of the a priori hydrophobic moment or the ability to form intramolecular salt bridges. Molecular dynamics (MD) simulations on two of the peptides suggest that sequence determines the insertion depth into the bilayer. The location of the two aspartate residues at the C-terminus of lysette-2 leads to a loss of helical content in the simulations, which correlates with faster desorption from the bilayer as compared to lysette. We also found a systematic deviation of the experimentally determined dissociation constant and that predicted by the Wimley–White interfacial hydrophobicity scale. The reason for the discrepancy remains unresolved but appears to correlate with a predominance of isoleucine over leucine residues in the lysette family of peptides.

Drug Conjugation Induced Modulation of Structural and Membrane Interaction Features of Cationic Cell-Permeable Peptides

“…Membrane-binding-induced folding of cationic peptides into amphipathic helices is a crucial step in their biological actions. Therefore, their structural modifications enhancing helix propensity often result in increased antibacterial and/or hemolytic activity [43][44][45]. INH conjugation did not change significantly or decrease membrane affinity of peptides with DPPC monolayer, except in the case of Buforin II (5-21), Dhvar4 and Transportan, where the penetration increased.…”

“…Membrane-binding-induced folding of cationic peptides into amphipathic helices is a crucial step in their biological actions. Therefore, their structural modifications enhancing helix propensity often result in increased antibacterial and/or hemolytic activity [43][44][45].…”

LL‐37 fragments have antimicrobial activity against Staphylococcus epidermidis biofilms and wound healing potential in HaCaT cell line

“…Besides, as FK‐12 and KR‐12 acted as inhibitory to biofilms even at concentrations below their MIC value, an additional explanation needs to be found. The death itself of some cells within the bacterial population and their consequent lysis, mediated by autolysin E, would release extracellular DNA and promote biofilm assembling in the remaining subpopulation . The hypothesis arises that the fragments and LL‐37 would inhibit the biofilm formation by halting the programed cell death of bacterial subpopulations, which in turn acted as a trigger for biofilm assembly.…”

“…It has been proposed that the pleiotropic functions of LL-37 are mapped on different regions of the peptide. The hydrophobic N-terminal [1][2][3][4][5][6][7][8][9][10][11][12][13] has been associated with oligomerization, hemolytic, and chemotactic properties, the main antimicrobial properties reside within the middle region [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] , whereas the C-terminal [32][33][34][35][36][37] is involved in the LL-37 tetramer formation at physiological pH. 11,12 The LL-37 tetramer is maintained in zwitterionic membranes, as is the case of human erythrocytes membranes.…”

Relative role(s) of leucine versus isoleucine in the folding of membrane proteins

“…For example, the antimicrobial peptides aurein 2.2 and 2.3—varying only in a single Leu/Ile—have differing activity against various bacterial species . Studies using peptides derived from δ‐lysin, an amphipathic peptide known to bind membrane surfaces, have provided insight that suggests peptides rich in Ile rather than Leu may bind lipid bilayers more efficiently . The DiMaio group, through a series of elegant experiments, have shown how Leu‐to‐Ile mutations and vice versa in synthetic TM domains can greatly impact receptor binding and alter receptor specificity .…”