¹⁹F NMR Analysis of the Antimicrobial Peptide PGLa Bound to Native Cell Membranes from Bacterial Protoplasts and Human Erythrocytes

Abstract

(19)F NMR is a unique tool to examine the structure of fluorine-labeled peptides in their native cellular environment, due to an exquisite sensitivity and lack of natural abundance background. For solid-state NMR analysis, we isolated native membranes from erythrocyte ghosts and bacterial protoplasts and prepared them as macroscopically oriented samples. They showed a high purity and quality of alignment according to (31)P NMR, and the membrane-bound antimicrobial peptide PGLa could be detected by (19)F NMR. The characteristic fingerprint splitting of its (19)F reporter group indicated that the peptide helix binds to the native membranes in a surface alignment, albeit with a higher affinity in the prokaryotic than the eukaryotic system.

Hydrophobic mismatch demonstrated for membranolytic peptides and their use as molecular rulers to measure bilayer thickness in native cells

“…CD showed that all peptides are mostly α-helical in DMPC/DMPG vesicles (Figure S1, Table 1). We have previously performed solid-state 19 F-NMR experiments in both DMPC/DMPG and in bacterial and erythrocyte membranes of several AMPs, and found the same structure and orientation of peptides in both DMPC/DMPG and in biological membranes5657, supporting the conclusion that the KIA peptides are α-helical also in biological membranes.…”

Antimicrobial Peptides can Enhance the Risk of Persistent Infections

“…All three helical molecules (with a length of around 20 amino acids) bind to lipid bilayers, where they can be surface-bound or obliquely immersed, depending on peptide concentration (Glaser et al, 2005; Bürck et al, 2008; Strandberg et al, 2009) and temperature (Afonin et al, 2008b). A fully inserted transmembrane state of these peptides has been associated with the formation of transient pores (Afonin et al, 2008b; Ieronimo et al, 2010). These have been shown to allow the escape of small metabolites and ions (Matsuzaki, 1998), thereby also decreasing the transmembrane proton gradient and as a result ATP generation.…”

Crown ether helical peptides are preferentially inserted in lipid bilayers as a transmembrane ion channels

“…Gramicidin A and alamethicin, both of which have a predominantly hydrophobic surface when folded, are generally inserted in a transmembrane alignment . Amphiphilic helices like magainin, on the other hand, are known to reside favorably on the membrane surface and tend to insert only transiently to self‐assemble as pores . These kind of membrane interactions of natural and biomimetic peptides open the door to the possibility to fight bacteria as well as cancer cells, and is of great interest for nanochemotherapy.…”