Helical Structure of Dermaseptin B2 in a Membrane-Mimetic Environment

Abstract

Dermaseptins are antimicrobial peptides from frog skin that have high membrane-lytic activity against a broad spectrum of microorganisms. The structure of dermaseptin B2 in aqueous solution, in TFE/water mixtures, and in micellar and nonmicellar SDS was analyzed by CD, FTIR, fluorescence, and NMR spectroscopy combined with molecular dynamics calculations. Dermaseptin B2 is unstructured in water, but helical conformations, mostly in segment 3-18, are stabilized by addition of TFE. SDS titration showed that dermaseptin B2 assumes nonhelical structures at SDS concentrations far below the critical micellar concentration and helical structures at micellar concentrations. Dermaseptin B2 bound to SDS micelles (0.4 mM peptide, 80 mM SDS) adopts a well-defined amphipathic helix between residues 11-31 connected to a more flexible helical segment spanning residues 1-8 by a flexible hinge region around Val9 and Gly10. Experiments using paramagnetic probes showed that dermaseptin B2 lies near the surface of SDS micelles and that residue Trp3 is buried in the SDS micelle, but close to the surface. A slow exchange equilibrium occurs at higher peptide/SDS ratios (2 mM peptide, 80 mM SDS) between forms having distinct sets of resonances in the N-terminal 1-11 segment. This equilibrium could reflect different oligomeric states of dermaseptin B2 interacting with SDS micelles. Structure-activity studies on dermaseptin B2 analogues showed that the N-terminal 1-11 segment is an absolute requirement for antibacterial activity, while the C-terminal 10-33 region is also important for full antibiotic activity.

Temporin-SHf, a New Type of Phe-rich and Hydrophobic Ultrashort Antimicrobial Peptide

“…Alternatively, the peptide may adopt more tilted orientations that would position the Phe 3 and Leu 4 residues deeply inside the micelle. Despite the fact that the peptide chain of temporin-SHf is very short, its mode of antimicrobial action involves binding and penetration into the bilayer, causing disruption of acyl chain packing, efflux of large molecules and microbial cell death, similar to that of many long AMPs (23,48,49). In terms of a mechanistic model, temporin-SHf is not long enough to form toroidal pores through the target membrane.…”

Conformation–activity relationship of a novel peptide antibiotic: Structural characterization of dermaseptin DS 01 in media that mimic the membrane environment

“…We can have a useful representation of the surface properties of the three representative peptides by building a contact surface of their structure and coloring it according to the electrostatic potential. Whereas for DS 01 in TFE we could use the experimental structure determined in the present work and for B2 a recently determined structure, 41 for dermaseptin S1 we built a homology model based on the coordinates of DS 01. While our manuscript was in preparation, an article describing the structure of B2 both in SDS micelles and in TFE/water appeared in the literature.…”

Dendrimers as Antibacterial Agents

“…They are an important part of the innate defense system, possessing a high potency and broad spectrum of activity against prokaryotic cells with only a minor impact on eukaryotic cells. Such properties raised some hope that natural antimicrobial peptides and their synthetic analogs may be adaptable for use in vivo as new generation antibiotics (Lequin et al, 2003;Papo & Shai, 2003;Powers & Hancock, 2003).…”