Dermaseptin S5: frog-skin natural germ-killer (DS5)
A natural peptide from South American leaf frog skin that kills bacteria, fungi, and parasites (including the one that causes Leishmania disease) by punching holes in their outer membranes; used only as a lab research tool.
A researcher, an agent, or an algorithm wrote down the sequence and picked a target to hit.
An AI model like OpenFold3 or AlphaFold built a 3D structure and scored how well it fits the binding site.
A second contributor repeated the computation on their own hardware and the scores matched.
A chemistry service or a researcher ordered the sequence, it was manufactured, and mass spectrometry confirmed the right molecule was produced.
A binding or activity measurement confirmed that it actually does what the computer predicted — or didn't.
What this is
Dermaseptin S5 (DS5, also Dermaseptin-S5 or DRS-S5) is a natural antimicrobial peptide found in the skin secretions of South American leaf frogs of the genus Phyllomedusa — the same family whose skin glands also produce the opioid peptide dermorphin (/card/pep-10694). It belongs to the dermaseptin family of cationic, lysine-rich peptides, roughly 27–34 residues long, that fold into an amphipathic α-helix on contact with microbial membranes and kill bacteria, fungi, and protozoan parasites by physically disrupting those membranes (Mor and colleagues, Biochemistry, 1994; Leite and colleagues, Comparative Biochemistry and Physiology Part A, 2008). DS5 is a preclinical research peptide: it has never been tested in humans, has no approved indication, and is studied primarily as a starting point for designing membrane-active anti-infectives. The stored sequence ALWKTLLKKVGTHLAGKAALGAAADKX (27 letters with a trailing X placeholder) represents the peptide backbone; the native peptide carries a C-terminal amide (-NH₂) cap that is not visible in the raw single-letter string and that protects the C-terminus from carboxypeptidases.
History
The dermaseptin family was first described in the early 1990s by the laboratories of Amram Mor and Pierre Nicolas, working on the skin secretions of Phyllomedusa tree frogs. The 1994 paper by Mor and colleagues in Biochemistry — "Structure, synthesis, and activity of Dermaseptin b, a novel vertebrate defensive peptide from frog skin: relationship with adenoregulin" — anchored the structural model that still defines the group: cationic, ~27–34 residue peptides that adopt an amphipathic α-helix on membranes. Two parallel research threads followed. Pierre and colleagues (European Journal of Biochemistry, 2000) and Chen and colleagues (Regulatory Peptides, 2003; Peptides, 2006) mapped out the precursor architecture, showing that the dermaseptin precursors share a conserved N-terminal preprosequence with the precursors of the opioid peptides dermorphin and the deltorphins — the same skin gland produces both families from related cDNAs. Vanhoye and colleagues (European Journal of Biochemistry, 2003) traced this precursor architecture back to a roughly 150-million-year-old ancestral gene with a conserved signal peptide but a hypermutable antimicrobial domain, which is why each Phyllomedusa species produces its own distinct dermaseptin cocktail.
DS5 itself sits within the S-series (S1–S5) from Phyllomedusa sauvagii. It has remained a reference compound for membrane-disruption biophysics and a comparator in structure–activity work on better-studied siblings such as dermaseptin S4 (Krugliak and colleagues, Antimicrobial Agents and Chemotherapy, 2000), rather than the lead of an independent drug-development program.
What it does
DS5 kills a broad range of microbes — Gram-positive and Gram-negative bacteria, yeasts and filamentous fungi, and protozoan parasites including Leishmania and Plasmodium — by tearing open their cell membranes (Leite and colleagues, 2008; Krugliak and colleagues, 2000; Ghosh and colleagues, Journal of Biological Chemistry, 1997). The peptide is largely disordered in water; on contact with the negatively charged outer surface of a microbial membrane it folds into an amphipathic α-helix, accumulates on the membrane, and either disorganizes the bilayer in a detergent-like "carpet" fashion or assembles into transient toroidal pores. Either way the membrane's electrochemical gradient collapses and the cell leaks ions and cytoplasmic contents.
Selectivity for microbes over host cells comes from chemistry, not specificity: bacterial and parasite membranes are richer in anionic lipids (phosphatidylglycerol, cardiolipin, lipopolysaccharide) and lack cholesterol, so the cationic peptide is drawn to them preferentially. That selectivity is relative, not absolute — at high enough concentrations dermaseptins damage mammalian cells too — and the therapeutic window is the central drug-development question for the whole family (Leite and colleagues, 2008). Because the mechanism is physical disruption of the membrane rather than inhibition of a specific enzyme, microbes have a hard time evading dermaseptins by point mutation; this is part of the long-running interest in the class as a response to antibiotic resistance.
Evidence
- Human: No published human trials. There are no human pharmacokinetic, safety, or efficacy data for DS5 in any indication.
- Animal: Limited. The native DS5 literature is dominated by in vitro assays; most in vivo work in the dermaseptin family has gone to engineered analogs of dermaseptin S4 (Krugliak and colleagues, 2000) rather than to DS5 itself.
- In vitro: Broad antimicrobial activity at low-micromolar concentrations against Gram-positive and Gram-negative bacteria, Candida and filamentous fungi, Leishmania promastigotes, and intraerythrocytic Plasmodium falciparum (Ghosh and colleagues, 1997; Krugliak and colleagues, 2000; Leite and colleagues, 2008). DS5 is reported to have low hemolytic activity against human red blood cells at antimicrobial concentrations relative to several of its siblings (Leite and colleagues, 2008), which is part of why it has been used as a scaffold for analog design.
Known effects
- Broad-spectrum antibacterial (Gram-positive and Gram-negative) — in vitro only
- Antifungal activity against Candida — in vitro only
- Anti-Leishmania activity (promastigotes) — in vitro; mechanism is direct parasite-membrane disruption
- Anti-Plasmodium activity (intraerythrocytic stages) — in vitro; demonstrated more extensively for the S-series sibling dermaseptin S3 (Ghosh and colleagues, 1997) and for dermaseptin S4 derivatives (Krugliak and colleagues, 2000)
- Lower hemolytic activity than several other dermaseptins at antimicrobial concentrations, in vitro (Leite and colleagues, 2008)
Safety signals
There is no human safety profile for DS5 — it has never been administered to humans in any published study. In vitro, DS5 is reported as having low hemolytic activity against human red blood cells at antimicrobial concentrations relative to several family members (Leite and colleagues, 2008), but membrane-disrupting peptides are cytotoxic to mammalian cells at high enough concentrations, and that ceiling is sequence- and context-dependent. The relative selectivity for microbial over mammalian membranes that DS5 shows in vitro is not the same thing as a characterized in vivo safety window.
Regulatory status
- US: Not approved. No Investigational New Drug (IND) application on record. Research compound only.
- EU: Not approved. No EMA marketing authorization or clinical trial authorization for any dermaseptin.
- WADA: Not listed; not relevant as a research peptide with no human use pathway.
DS5 is a laboratory peptide; preparations from research-chemical channels are not authorized for human use and carry no identity, purity, sterility, or endotoxin guarantees.
Related peptides
- Dermorphin (/card/pep-10694) — also from Phyllomedusa skin, but a μ-opioid receptor agonist rather than an antimicrobial peptide; encoded by precursors that share an N-terminal preprosequence with the dermaseptins (Pierre and colleagues, 2000; Vanhoye and colleagues, 2003).
- LL-37 (/card/pep-00002) — the human cathelicidin antimicrobial peptide; a cationic amphipathic α-helix with the same membrane-disruption logic as the dermaseptins, but evolved independently in mammalian innate immunity.
- Magainin — antimicrobial α-helix from the skin of the African clawed frog Xenopus laevis; the canonical example of an amphibian AMP outside the Phyllomedusa lineage.
Mechanism
DS5 is a cationic, lysine-rich peptide of approximately 28 residues that is largely unstructured in aqueous solution and adopts an amphipathic α-helical conformation upon contact with lipid bilayers. Electrostatic attraction to anionic phospholipid headgroups (phosphatidylglycerol, cardiolipin) and to lipopolysaccharide recruits the peptide to the outer leaflet of a microbial membrane, where the hydrophobic and hydrophilic faces of the helix align with the membrane environment. Peptide accumulates on the outer leaflet until a critical local density is reached, at which point it either disorganizes the bilayer in a "carpet"-like detergent fashion or assembles into transient toroidal pores — in either case the transmembrane gradient collapses, ions and small metabolites leak across, and the cell dies (Leite and colleagues, 2008). The same mechanism accounts for activity against bacteria, yeasts, Leishmania promastigotes, and intraerythrocytic Plasmodium stages, since all share negatively charged surface membranes that mammalian cell membranes do not.
Two further mechanism notes are worth flagging. First, dermaseptins in the native frog secretion appear to act as a cocktail rather than as individual agents — published work in the family has reported synergy between dermaseptin variants in combined assays, consistent with the hypothesis that the cocktail composition matters (Mor and colleagues, 1994). Second, the dermaseptin precursor architecture is the same one that generates the opioid peptides dermorphin and the deltorphins in the same skin glands (Pierre and colleagues, 2000; Vanhoye and colleagues, 2003), so the same animal lineage produces two pharmacologically unrelated peptide families from related cDNAs — a curiosity of amphibian skin biology that recurs throughout this literature.
Open questions
- Whether the in vitro selectivity for microbial over mammalian membranes survives at in vivo concentrations and at the doses needed for systemic antimicrobial activity — the central drug-development problem for every cationic amphipathic AMP, not specific to DS5.
- Whether DS5's anti-Leishmania activity can be translated into a topical or systemic preclinical efficacy signal, given that most in vivo dermaseptin work has focused on dermaseptin S4 analogs rather than DS5 (Krugliak and colleagues, 2000).
- Whether structural minimization or stabilization (truncation, D-amino acid substitution, lipidation) can preserve the membrane-disruption potency of DS5 while widening its therapeutic window — the medicinal-chemistry program that most of the dermaseptin field has pursued on DS4 has not been extensively replicated on DS5.
- Whether the synergy reported among native dermaseptins (Mor and colleagues, 1994) reflects a deployable design principle for combination AMP formulations or an artifact of the in vitro assays used to detect it.
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Could a single flexible point in the DS5 helix control how deeply the peptide buries itself in bacterial membranes, determining whether it kills Gram-positive or Gram-negative bugs?
If true, chemists could lock or adjust that hinge to make versions of DS5 that specifically target dangerous Gram-negative bacteria like E. coli or Klebsiella, which are increasingly resistant to antibiotics and cause life-threatening hospital infections.
Do parasites like Leishmania attract DS5 to their surface more strongly than human cells do, because the parasites display a specific membrane fat on the outside that human cells keep hidden?
If confirmed, this mechanism would point to a broad strategy for designing selective antiparasitic peptides, potentially improving treatment for neglected tropical diseases that affect tens of millions of people in low-income countries with few affordable options.
If the open end of DS5 were extended with a few extra charged building blocks, could the peptide act as a vehicle to smuggle antifungal drugs into resistant Candida cells that would otherwise pump them out?
Candida auris now causes treatment-resistant hospital outbreaks with mortality rates above 30%. A peptide that smuggles drugs past resistance barriers could restore the effectiveness of existing antifungals, giving clinicians a new tool without requiring entirely new drug development.
Could DS5 penetrate and disrupt the sticky biofilm that bacteria form on catheters and implants, where ordinary antibiotics cannot reach them?
Biofilm infections on medical implants kill thousands of patients each year and often require surgically removing the device. A peptide coating that prevented biofilm formation could protect patients from this devastating complication without any need for systemic antibiotic treatment.
Does the unusual number and spacing of positively charged amino acids in DS5 help the peptide target the type of membrane fat found in fungi but not in human cells?
Fungal infections kill over 1.5 million people per year, and options are limited. If DS5 can selectively target fungal membranes, derivatives could provide a new class of topical or wound antifungals with less risk of harming human tissue.
▸3-letter notation
▸citationbibtex
@peptide{pep10966,
sequence = {ALWKTLLKKVGTHLAGKAALGAAADKX},
target = {},
author = {peptidemodel},
year = {2026},
status = {designed}
}