Dermaseptin S9, an α-Helical Antimicrobial Peptide with a Hydrophobic Core and Cationic Termini

Abstract

The dermaseptins S are closely related peptides with broad-spectrum antibacterial activity that are produced by the skin of the South American hylid frog, Phyllomedusa sauvagei. These peptides are polycationic (Lys-rich), alpha-helical, and amphipathic, with their polar/charged and apolar amino acids on opposing faces along the long axis of the helix cylinder. The amphipathic alpha-helical structure is believed to enable the peptides to interact with membrane bilayers, leading to permeation and disruption of the target cell. We have identified new members of the dermaseptin S family that do not resemble any of the naturally occurring antimicrobial peptides characterized to date. One of these peptides, designated dermaseptin S9, GLRSKIWLWVLLMIWQESNKFKKM, has a tripartite structure that includes a hydrophobic core sequence encompassing residues 6-15 (mean hydrophobicity, +4.40, determined by the Liu-Deber scale) flanked at both termini by cationic and polar residues. This structure is reminiscent of that of synthetic peptides originally designed as transmembrane mimetic models and that spontaneously become inserted into membranes [Liu, L., and Deber, C. M. (1998) Biopolymers 47, 41-62]. Dermaseptin S9 is a potent antibacterial, acting on gram-positive and gram-negative bacteria. The structure of dermaseptin S9 in aqueous solution and in TFE/water mixtures was analyzed by circular dichroism and two-dimensional NMR spectroscopy combined with molecular dynamics calculations. Dermaseptin S9 is aggregated in water, but a monomeric nonamphipathic alpha-helical conformation, mostly in residues 6-21, is stabilized by the addition of TFE. These results, combined with membrane permeabilization assays and surface plasmon resonance analysis of the peptide binding to zwitterionic and anionic phospholipid bilayers, demonstrate that spatial segregation of hydrophobic and hydrophilic/charged residues on opposing faces along the long axis of a helix is not essential for the antimicrobial activity of cationic alpha-helical peptides.

Synthesis and antimicrobial activity of dermaseptin S1 analogues

“…A small but consistent increase in antimicrobial activity was observed for compound DS1(1-29)-NH 2 , whilst deletion of residues beyond position 15 at the C-terminus produces a marked decrease in biological activity. Having selected peptide DS1(1-15)-NH 2 as a template for further structure-activity investigations, we focused on the importance of the highly conserved tryptophan in position 3 8,18 on antimicrobial activity. Replacement of the indole with a naphthyl moiety generated compounds 7 and 8 that showed an antimicrobial potency comparable to that of the reference DS1(1-15)-NH 2 .…”

“…Amongst possible single residue changes we focused on position 3 (Trp 3 ) to assess the importance of the dermaseptin conserved indole moiety on bioactivity. 18 Here we report the design, synthesis and biological evaluation of 15 DS1 analogues.…”

In Vitro Activities of Dermaseptins K 4 S 4 and K 4 K 20 S 4 against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa Planktonic Growth and Biofilm Formation

“…Other studies demonstrated that dermaseptin K 4 K 20 S 4 had good antimicrobial activity in vivo, with no toxicity, in mice (30). The combination of the deletion of 12 C-terminal residues with the substitution of methionine by lysine at position 4 in K 4 S 4 (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16), the deletion of 5 N-terminal residues in dermaseptin S 4 , and the reduction of positive charges by substituting methionine by aspartic acid at positions 4 and 20 were reported to induce marked decreases in antimicrobial activity in comparison with K 4 K 20 S 4 . It can be concluded from these observations that increasing the net positive charge of the peptide without shortening its sequence Biofilm-forming S. aureus, P. aeruginosa, and E. coli strains were grown in 96-well polystyrene plates, and the biofilms formed were exposed to the peptides at 2ϫ MIC for 24 h. Control, negative-control wells containing only the appropriate medium for each strain; Polymyxin, positive-control wells.…”

“…They all have a conserved Trp residue at position 3, an AG(A)KAAL(V/G)G(N/K)AV(A) consensus motif in the middle region, and a positive charge attributable to the presence of Lys residues that punctuate an alternating hydrophobic-hydrophilic sequence (13). New members of the dermaseptin S family (S 9 to S 11 ) that do not resemble any of the natural antimicrobial peptides characterized to date have recently been identified and cloned from a skin secretion-derived cDNA library (15). In fact, some dermaseptins show marked abilities to inhibit microbial cells efficiently, rapidly, and irreversibly without toxic effects on mammalian cells.…”

Purification and characterization of one novel cationic antimicrobial peptide from skin secretion of Bufo kavirensis

“…The skin of amphibian has glands that are rich resources for antimicrobial peptides [5,6]. Antimicrobial peptides are secreted by these dermal glands and they play a defensive role against harmful microorganisms [5,7].To date, a lot of antimicrobial peptides such as berevinins, temporins, magainin and dermaseptins have been isolated and purified from amphibians [8][9][10][11][12][13][14]. These peptides have several activity such as antibacterial, antifungal, antiviral, anticancer and spermicidal [9,[15][16][17][18].…”