Structural and Dynamic Insights of the Interaction between Tritrpticin and Micelles: An NMR Study

Abstract

A large number of antimicrobial peptides (AMPs) acts with high selectivity and specificity through interactions with membrane lipid components. These peptides undergo complex conformational changes in solution; upon binding to an interface, one major conformation is stabilized. Here we describe a study of the interaction between tritrpticin (TRP3), a cathelicidin AMP, and micelles of different chemical composition. The peptide's structure and dynamics were examined using one-dimensional and two-dimensional NMR. Our data showed that the interaction occurred by conformational selection and the peptide acquired similar structures in all systems studied, despite differences in detergent headgroup charge or dipole orientation. Fluorescence and paramagnetic relaxation enhancement experiments showed that the peptide is located in the interface region and is slightly more deeply inserted in 1-myristoyl-2-hydroxy-sn-glycero-3-phospho-1 0 -rac-glycerol (LMPG, anionic) than in 1-lauroyl-2-hydroxy-sn-glycero-3-phosphocholine (LLPC, zwitterionic) micelles. Moreover, the tilt angle of an assumed helical portion of the peptide is similar in both systems. In previous work we proposed that TRP3 acts by a toroidal pore mechanism. In view of the high hydrophobic core exposure, hydration, and curvature presented by micelles, the conformation of TRP3 in these systems could be related to the peptide's conformation in the toroidal pore.

Dissecting the mechanism of action of actinoporins. Role of the N-terminal amphipathic α-helix in membrane binding and pore activity of sticholysins I and II

“…Binding of sticholysins N-terminal peptides to bilayers can be envisioned as the initial step in the mechanism of pore formation, comprising acquisition of secondary structure and helix interaction with the water-membrane interface. As proposed by Bozelli et al [ 61 ] and Santos et al [ 62 ], due to the looser packing of lipids in micelles, which possibly resembles that in the toroidal pore structure, where the lipids are in positive curvature, the interaction with micelles would mimic the topography of the toxin’s N-terminal segment in the toroidal pore region. The differences between bilayer-bound and micelle-bound peptides helical content ( Table 2 ) would, then, be related to the peptides conformation at the membrane surface and in the pore region, respectively.…”

Insights Into the Micelle-Induced β-Hairpin-to-α-Helix Transition of a LytA-Derived Peptide by Photo-CIDNP Spectroscopy

“…As shown in Figure 3, in the presence of 5 mM of DPC micelles, the NMR signals corresponding to W241, W248, Y249, and Y250 were broadened and slightly shifted. This is evidence of a strong interaction between micelle and peptide [21,30]. Whereas this broadening hampers photo-CIDNP studies in the presence of DPC concentrations between 5 and 30 mM (see Figure 2), using 2 mM DPC is enough for understanding the conformational change by photo-CIDNP experiments.…”

A Dynamic Overview of Antimicrobial Peptides and Their Complexes

“…Using NMR to evaluate the structure of TRP3 in micelles with various chemical features reveals interactions occurred through conformational selection, stabilizing similar structures despite differences in detergent headgroups or dipole orientations [ 78 ]. These data also reveal the imperative constraint of the WWW-F motif in the TRP3 structure, acquired at interfaces, and show that pre-organization in the free state is crucial for membrane interaction.…”