(19)F NMR screening of unrelated antimicrobial peptides shows that membrane interactions are largely governed by lipids.
Many amphiphilic antimicrobial peptides permeabilize bacterial membranes via successive steps of binding, re-alignment and/or oligomerization. Here, we have systematically compared the lipid interactions of two structurally unrelated peptides: the cyclic β-pleated gramicidin S (GS), and the α-helical PGLa. (19)F NMR was used to screen their molecular alignment in various model membranes over a wide range of temperatures. Both peptides were found to respond to the phase state and composition of these different samples in a similar way. In phosphatidylcholines, both peptides first bind to the bilayer surface. Above a certain threshold concentration they can re-align and immerse more deeply into the hydrophobic core, which presumably involves oligomerization. Re-alignment is most favorable around the lipid chain melting temperature, and also promoted by decreasing bilayer thickness. The presence of anionic lipids has no influence in fluid membranes, but in the gel phase the alignment states are more complex. Unsaturated acyl chains and other lipids with intrinsic negative curvature prevent re-alignment, hence GS and PGLa do not insert into mixtures resembling bacterial membranes, nor into bacterial lipid extracts. Cholesterol, which is present in high concentrations in animal membranes, even leads to an expulsion of the peptides from the bilayer and prevents their binding altogether. However, a very low cholesterol content of 10% was found to promote binding and re-alignment of both peptides. Overall, these findings show that the ability of amphiphilic peptides to re-align and immerse into a membrane is determined by the physico-chemical properties of the lipids, such as spontaneous curvature. This idea is reinforced by the remarkably similar behavior observed here for two structurally unrelated molecules (with different conformation, size, shape, charge), which further suggests that their activity at the membrane level is largely governed by the properties of the constituent lipids, while the selectivity towards different cell types is additionally ruled by electrostatic attraction between peptide and cell surface. This article is part of a Special Issue entitled: Interfacially Active Peptides and Proteins. Guest Editors: William C. Wimley and Kalina Hristova.
Karlsruhe Institute of Technology (KIT), Institute of Biological Interfaces (IBG-2), POB 3640, 76021 Karlsruhe, Germany.
Sergii
S
Afonin
Institute of Biochemistry and Biophysics, Friedrich-Schiller-Universität Jena, Hans-Knöll-Str. 2, 07745 Jena, Germany.
Ralf W
RW
Glaser
EMBL - European Molecular Biology Laboratory, Structural and Computational Biology, Meyerhofstr. 1, 69117 Heidelberg, Germany.
Carsten
C
Sachse
Institute of Molecular Science (ICMol), University of Valencia, C/Catedrático José Beltrán, 2, 46980 Paterna, Valencia, Spain.
Jesús
J
Salgado
Karlsruhe Institute of Technology (KIT), Institute of Biological Interfaces (IBG-2), POB 3640, 76021 Karlsruhe, Germany.
Parvesh
P
Wadhwani
Karlsruhe Institute of Technology (KIT), Institute of Biological Interfaces (IBG-2), POB 3640, 76021 Karlsruhe, Germany; Karlsruhe Institute of Technology (KIT), Institute of Organic Chemistry, Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany. Electronic address: Anne.Ulrich@kit.edu.
Anne S
AS
Ulrich
D000595:Amino Acid Sequence; D001419:Bacteria / Q000737:chemistry / Q000187:drug effects; D002462:Cell Membrane / Q000737:chemistry* / Q000187:drug effects; D006096:Gramicidin / Q000737:chemistry* / Q000494:pharmacology; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry*; D008563:Membrane Lipids / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular; D011498:Protein Precursors / Q000737:chemistry* / Q000494:pharmacology; D017433:Protein Structure, Secondary
D008051:Lipid Bilayers; D008563:Membrane Lipids; C088254:PGLa prepropeptide; D011498:Protein Precursors; D006096:Gramicidin
Amphiphilic antimicrobial peptides; Bacterial membranes; Lipid composition; Re-alignment in membrane; Solid state (19)F NMR structure analysis; Spontaneous curvature