Dynamic Structure and Orientation of Melittin Bound to Acidic Lipid Bilayers, As Revealed by Solid-State NMR and Molecular Dynamics Simulation

Abstract

Melittin is a venom peptide that disrupts lipid bilayers at temperatures below the liquid-crystalline to gel phase transition temperature (T). Notably, the ability of melittin to disrupt acidic dimyristoylphosphatidylglycerol (DMPG) bilayers was weaker than its ability to disrupt neutral dimyristoylphosphatidylcholine bilayers. The structure and orientation of melittin bound to DMPG bilayers were revealed by analyzing the C chemical shift anisotropy of [1-C]-labeled melittin obtained from solid-state C NMR spectra.C chemical shift anisotropy showed oscillatory shifts with the index number of residues. Analysis of the chemical shift oscillation properties indicated that melittin bound to a DMPG membrane adopts a bent α-helical structure with tilt angles for the N- and C-terminal helices of -32 and +30°, respectively. The transmembrane melittin in DMPG bilayers indicates that the peptide protrudes toward the C-terminal direction from the core region of the lipid bilayer to show a pseudotransmembrane bent α-helix. Molecular dynamics simulation was performed to characterize the structure and interaction of melittin with lipid molecules in DMPG bilayers. The simulation results indicate that basic amino acid residues in melittin interact strongly with lipid head groups to generate a pseudo-transmembrane alignment. The N-terminus is located within the lipid core region and disturbs the lower surface of the lipid bilayer.

Dynamic membrane interactions of antibacterial and antifungal biomolecules, and amyloid peptides, revealed by solid-state NMR spectroscopy

“…In this case, an axially symmetric powder pattern is observed as shown in lecithin-melittin bilayer systems (Fig. 1(b) and (g)) [15,20,21]. …”

“…Solid-state NMR is particularly well suited for elucidating the dynamics, topologies, orientations, and high resolution structures of peptides in the lipid bilayer environment using membrane mimetics such as lipid vesicles, bicelles or lipid nanodiscs/macrodiscs. While several studies have reported valuable structural and functional insights into a variety of AMPs (including magainins, MSI-78, LL-37, pardaxin, protegrin and other designed peptides), the use of chemical shift oscillation analysis in elucidating the detailed structure and orientation of the membrane bound state of antibacterial peptides such as melittin [15,20,21], bonbolitin II [49], lactoferrampin [45] and alamethicin [50] reported in the literature are highlighted below.…”

“…The isotropic 13 C chemical shifts of the [l- 13 C]Gly3, [l- 13 C]Val5, [l- 13 C]Glyl2, [l- 13 C]Leul6, and [l- 13 C]Ile20 residues in melittin were determined to be 172.7, 175.2, 171.6, 175.6, and 174.8 ppm, respectively, indicating that all of these residues are involved in the α-helix [15,20,21]. …”

“…The dynamic structures of melittin bound to dipalmitoylphosphatidylcholine (DPPC), dilauroylphosphatidylcholine (DLPC) and dίmyristoylphosphatίdylgrycerol (DMPG) were investigated by analyzing the 13 C anisotropic and isotropic chemical shifts of selectively 13 C-labeled carbonyl carbons of melittin under static and MAS conditions [15,21]. Axially symmetric chemical-shift powder patterns were observed for [l- 13 C]Gly3, [l- 13 C]Ala4, [l- 13 C]Val5, [l- 13 C]Glyl2, [l- 13 C]Leul6, and [l- 13 C]Ile20.…”

“…(B): 13 C chemical shift powder patterns of the [l- 13 C]Gly3-, [l- 13 C]Ala4-, [l- 13 C]Val5, [1- 13 C] Leu16, [l- 13 C]Ilel7, and [l- 13 C]Ile20-melittins-DMPG bilayer systems at 40 °C [21]. …”