Membrane thickening by the antimicrobial peptide PGLa.
Using x-ray diffraction, solid-state 2H-NMR, differential scanning calorimetry, and dilatometry, we have observed a perturbation of saturated acyl chain phosphatidylglycerol bilayers by the antimicrobial peptide peptidyl-glycylleucine-carboxyamide (PGLa) that is dependent on the length of the hydrocarbon chain. In the gel phase, PGLa induces a quasi-interdigitated phase, previously reported also for other peptides, which is most pronounced for C18 phosphatidylglycerol. In the fluid phase, we found an increase of the membrane thickness and NMR order parameter for C14 and C16 phosphatidylglycerol bilayers, though not for C18. The data is best understood in terms of a close hydrophobic match between the C18 bilayer core and the peptide length when PGLa is inserted with its helical axis normal to the bilayer surface. The C16 acyl chains appear to stretch to accommodate PGLa, whereas tilting within the bilayer seems to be energetically favorable for the peptide when inserted into bilayers of C14 phosphatidylglycerol. In contrast to the commonly accepted membrane thinning effect of antimicrobial peptides, the data demonstrate that pore formation does not necessarily relate to changes in the overall bilayer structure.
Pabst
Georg
G
Institute of Biophysics and Nanosystems Research, Austrian Academy of Sciences, Graz, Austria.
Grage
Stephan L
SL
Danner-Pongratz
Sabine
S
Jing
Weiguo
W
Ulrich
Anne S
AS
Watts
Anthony
A
Lohner
Karl
K
Hickel
Andrea
A
D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D002152:Calorimetry, Differential Scanning; D002462:Cell Membrane / Q000737:chemistry* / Q000187:drug effects*; D006358:Hot Temperature; D008051:Lipid Bilayers / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D010715:Phosphatidylglycerols / Q000737:chemistry; D053838:Scattering, Small Angle; D013696:Temperature; D013816:Thermodynamics; D014961:X-Ray Diffraction
D023181:Antimicrobial Cationic Peptides; D008051:Lipid Bilayers; D010715:Phosphatidylglycerols; C045866:peptide-Gly-Leu-amide; C084352:distearoyl phosphatidylglycerol; C030345:1,2-dipalmitoylphosphatidylglycerol