Nitrogen-14 Solid-State NMR Spectroscopy of Aligned Phospholipid Bilayers to Probe Peptide−Lipid Interaction and Oligomerization of Membrane Associated Peptides

Abstract

Characterization of the oligomerization of membrane-associated peptides is important to understand the folding and function of biomolecules like antimicrobial peptides, fusion peptides, amyloid peptides, toxins, and ion channels. However, this has been considered to be very difficult, because the amphipathic properties of the constituents of the cell membrane pose tremendous challenges to most commonly used biophysical techniques. In this study, we present the application of a simple (14)N solid-state NMR spectroscopy of aligned model membranes containing a phosphatidyl choline lipid to investigate the oligomerization of membrane-associated peptides. Since the near-symmetric nature of the choline headgroup of a phosphocholine lipid considerably reduces the (14)N quadrupole coupling, there are significant practical advantages in using (14)N solid-state NMR experiments to probe the interaction of peptide or protein with the surface of model membranes. Experimental results for several membrane-associated peptides are presented in this paper. Our results suggest that the experimentally measured (14)N quadrupole splitting of the lipid depends on the peptide-induced changes in the electrostatic potential of the lipid bilayer surface and therefore on the nature of the peptide, peptide-membrane interaction, and peptide-peptide interaction. It is inferred that the membrane orientation and oligomerization of the membrane-associated peptides can be measured using (14)N solid-state NMR spectroscopy.

Structural effects of tachyplesin I and its linear derivative on their aggregation and mobility in lipid bilayers

“…These findings agree well with experimental observations of the immobilization of linear TPA4, as well as support the experimental suggestions that the aggregated ␤-strands of TPA4 cannot diffuse as fast as individual TP-I molecules [15]. These also imply that the oligomerization of those ␤-strands may significantly influence the antimicrobial activity of TP-I, as also observed in the experiments with ␣-helical magainin and their derivatives [41][42][43] and our previous simulations [44]. In this work, our simulations offer insights into the relationship of the peptide structure, aggregation, and mobility in lipid bilayers, but not antimicrobial activity.…”

Does Cholesterol Play a Role in the Bacterial Selectivity of Antimicrobial Peptides?

“…In addition, substantial progress has been in understanding the molecular determinants of AMP activity. For example, recent studies have shown the ability to form oligomeric aggregates in the cell membrane enhances the potency of an AMP (Toke et al, 2004; Tremouilhac et al, 2006; Marquette et al, 2008; Ramamoorthy et al, 2008; Strandberg et al, 2008). Studies have also shown that the presence of d-amino acids (Mangoni et al, 2006) and disulfide bridges (Dhople et al, 2006) can enhance resistance against proteolytic degradation without affecting the antimicrobial activity.…”

Direct detection of nitrogen-14 in solid-state NMR spectroscopy

“…(indicating a change in the membrane surface potential) while the channel-forming peptides did not, opening up the possibility of using this approach to probe the location and orientation of proteins with respect to the membrane [211].…”