Orientation and Dynamics of an Antimicrobial Peptide in the Lipid Bilayer by Solid-State NMR Spectroscopy

Abstract

The orientation and dynamics of an 18-residue antimicrobial peptide, ovispirin, has been investigated using solid-state NMR spectroscopy. Ovispirin is a cathelicidin-like model peptide (NH(2)-KNLRRIIRKIIHIIKKYG-COOH) with potent, broad-spectrum bactericidal activity. (15)N NMR spectra of oriented ovispirin reconstituted into synthetic phospholipids show that the helical peptide is predominantly oriented in the plane of the lipid bilayer, except for a small portion of the helix, possibly at the C-terminus, which deviates from the surface orientation. This suggests differential insertion of the peptide backbone into the lipid bilayer. (15)N spectra of both oriented and unoriented peptides show a reduced (15)N chemical shift anisotropy at room temperature compared with that of rigid proteins, indicating that the peptide undergoes uniaxial rotational diffusion around the bilayer normal with correlation times shorter than 10(-4) s. This motion is frozen below the gel-to-liquid crystalline transition temperature of the lipids. Ovispirin interacts strongly with the lipid bilayer, as manifested by the significantly reduced (2)H quadrupolar splittings of perdeuterated palmitoyloleoylphosphatidylcholine acyl chains upon peptide binding. Therefore, ovispirin is a curved helix residing in the membrane-water interface that executes rapid uniaxial rotation. These structural and dynamic features are important for understanding the antimicrobial function of this peptide.

Molecular dynamics simulations of helical antimicrobial peptides in SDS micelles: What do point mutations achieve?

“…In isolation from other peptides, a strongly amphipathic helix like OVIS is more prone to bind to the interfacial region, with its hydrophobic face embedded in the membrane core, and the polar helical region exposed to the solvent and/or interacting with the lipid headgroups. Yamaguchi et al 31 proposed a similar model from NMR experiments. The equilibrium average binding conformation of OVIS is in agreement with the experimentally predicted orientation of the peptide (Figure 3).…”

“…Solid-state NMR 31 and the proton inverse detected deuteron (PRIDE) NMR technique 36 indicate that ovispirin prefers to bind nearly parallel to the membrane-water interface (this corresponds to the final simulation conformation) and is not positioned across the bilayer (this corresponds to the starting simulation configuration). In both experiments, the peptide was reconstituted in lipid vesicles composed of (POPC: palmitoyloleoyl-phosphatidylcholine, POPG: palmitoyl-oleoyl-phosphatidylglycerol) lipids in a 3:1 ratio.…”

“…NMR experiments do suggest the possibility of formation of a C-terminal bend in OVIS when bound to bilayers. 31 This might be manifest in the slight deviation at position 13. However, this deviation is only on the order of ∼10°and is comparable to the magnitude of the fluctuations (error bars in Figure 4).…”

Structure and dynamics of cationic membrane peptides and proteins: Insights from solid‐state NMR

“…1(c)]. Both global backbone motion [29][30][31] and local segmental motions 6 are common in antimicrobial and CPPs due to the low molecular weights of these peptides and the fluidity of the lipid membrane. 32 With increasing ability to detect motion by NMR, it is now recognized that even larger membrane proteins such as seven transmembrane (TM)-helix proteins can undergo motions of sizeable amplitudes on the NMR timescale.…”

Antimicrobial peptides from amphibians

“…AMPs such as ovispirin rest on the surface of the cytoplasm (116)(117)(118). When the concentrations increase, they destroy the cytoplasm in a detergent manner and form micelles.…”