pe
pep-05597 v1 CC-BY-SA-4.0

Beta-defensin 131A antimicrobial peptide

A synthetic peptide that kills or stops the growth of bacteria; used only as a lab research tool.

statusbioassayed targetANTIMICROBIAL length57 aa refs3
antimicrobial
EARLY ENTRY This candidate is newly indexed — supporting evidence is still being added. Have a paper or data point? Contribute below.
status 2 / 5 · 0 verified on platform
prediction metrics boltz-2 2.2.1
ipTM0.000
pTM0.573
avg pLDDT79.1
ranking score0.747
STRUCTURE · PEP-05597 × ANTIMICROBIAL
ranking0.747
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RECEPTOR UNKNOWN
peptide conformation only · no target structure
target interface 4.5Å peptide drag rotate · ctrl+scroll zoom · right-click pan
sequence57 aa
151015202530354045505557
FFSLFKARTLFFKDTCSLE GYTCRMKCNADEHAIRYCT DWTICCKEKKIRLKKRKKW
in the news 6 articles
Hypotheses6 directions▾ collapse

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.

openupdated 2026-06-05

Could we strip out the costly, hard-to-make structural knots in this peptide and still get a working antibiotic?

Natural defensive peptides rely on elaborate molecular scaffolding that is expensive and fragile to manufacture. If the straightforward, positively charged tail of this peptide does the bacteria-killing work on its own, simpler and cheaper versions could be made at scale, which could matter for developing affordable antibiotics.

The hypothesis
The dense cationic C-terminal tail (KEKKIRLKKRKKW) of pep-05597 drives membrane disruption independently of its six cysteine residues, such that a disulfide-bond-free analog retains full bactericidal activity through electrostatic docking and lipid bilayer perturbation alone.
Why it’s plausible
The sequence contains six cysteines (C16, C22, C27, C37, C42, C43) that in canonical beta-defensins form a triple-disulfide scaffold stabilizing the beta-sheet core. However, the axis hit from 10.1074/jbc.M709238200 reports that cysteine-alkylated or cysteine-to-alanine beta-defensin mutants remain strongly antimicrobial, and N-terminal fragments with no disulfides retain potency. The C-terminal segment of pep-05597 is uniquely enriched in lysine and arginine residues (seven basic residues in the last 13 positions), which could electrostatically engage negatively charged bacterial lipopolysaccharide or phosphatidylglycerol without structural dependence on the disulfide core.
Why it matters
If the cysteine scaffold is dispensable, simplified linear analogs could be synthesized at far lower cost and with greater protease resistance than the full-length disulfide-containing peptide, directly addressing the manufacturing cost barrier cited in 10.1038/nbt1267.
Plausibility.78
Novelty.27
Impact.77
Basis · grounding2 papers · 1 computed/note
[1]
paper
Full-length beta-defensin peptides with alkylated cysteines or cysteine-to-alanine substitutions are still strongly antimicrobial; N-terminal fragments display potent antimicrobial activity independent of disulfide bonds.
doi: 10.1074/jbc.m709238200
[2]
sequenceC-terminal segment KEKKIRLKKRKKW contains seven basic residues in 13 positions, providing an unusually high local cationic density.
[3]
paper
Cationic AMPs adopt amphipathic conformations that allow interaction with negatively charged bacterial membranes via electrostatic attraction.
doi: 10.1177/0022034516679973
openupdated 2026-06-05

Could this peptide break through the thick, waxy coating that makes tuberculosis so hard to treat?

Drug-resistant TB kills hundreds of thousands of people each year, and few new treatments are in the pipeline. If this peptide can pierce the unusually tough outer layer of the TB bacterium without harming the immune cells fighting the infection, it could become a lead candidate for a new class of TB drug.

The hypothesis
pep-05597 is active against Mycobacterium tuberculosis at concentrations non-toxic to human macrophages, because its beta-defensin-like scaffold can penetrate the mycobacterial outer lipid membrane in a manner analogous to predicted beta-defensins identified as tuberculocidal candidates.
Why it’s plausible
The clinical-translation axis hit from 10.1002/prot.25785 specifically states that predicted beta-defensin peptides may help identify agents effective against M. tuberculosis, including multidrug-resistant strains. pep-05597 is a designed artificial beta-defensin with hallmark cationic and amphipathic features (per 10.1042/BJ20082242). Mycobacteria are notoriously resistant to conventional antibiotics partly due to their thick waxy cell wall, but cationic peptides can disrupt mycolic acid-rich membranes. The high charge density and hydrophobic Phe/Leu residues in pep-05597 are consistent with the amphipathic character needed for membrane intercalation into mycobacterial envelopes.
Why it matters
MDR-TB represents a critical unmet medical need; a designed peptide with tuberculocidal activity would be a significant therapeutic advance, and characterizing pep-05597 in this context is supported directly by the clinical-translation evidence in the bundle.
Plausibility.54
Novelty.37
Impact.80
Basis · grounding2 papers · 1 computed/note
[1]
paper
Predicted beta-defensin peptides from different sources may help identify and develop new antimicrobial agents effective against multidrug-resistant M. tuberculosis.
doi: 10.1002/prot.25785
[2]
paper
pep-05597 is a designed artificial beta-defensin incorporating hallmark amphipathic and cationic features of natural defensins.
doi: 10.1042/bj20082242
[3]
sequenceSequence contains bulky hydrophobic residues (F, L, W) interspersed with cationic residues, forming a plausible amphipathic character consistent with membrane-active peptides.
openupdated 2026-06-05

If we lock this peptide onto a tiny particle so bacteria cannot pump it out, does it stay effective against resistant bugs?

Many bacteria defeat antibiotics by actively pumping them out before they cause damage. Attaching the peptide to a nanoparticle surface could block that escape route, potentially restoring killing power against otherwise resistant strains, which would be useful in hospital settings where multidrug-resistant infections are rising.

The hypothesis
Immobilizing pep-05597 on nanoparticles via its N-terminal hydrophobic segment (FFSLFK) preserves bactericidal activity while abolishing susceptibility to bacterial efflux pumps, because surface-tethered presentation prevents cytoplasmic uptake that is required for efflux-mediated resistance.
Why it’s plausible
The axis hit from 10.1177/0022034516679973 states that AMPs acting intracellularly are susceptible to active efflux, and that immobilized AMPs can screen for surface-active peptides not susceptible to efflux pumps. The N-terminal segment of pep-05597 (FFSLFK) contains hydrophobic residues well-suited for surface tethering via the N-terminus while leaving the active cationic C-terminal region free for membrane engagement. This approach directly addresses the efflux resistance mechanism cited in the literature.
Why it matters
Efflux-resistant nano-immobilized formulations of pep-05597 would retain efficacy against multidrug-resistant organisms where efflux pumps have neutralized other AMPs, representing a practical engineering path to clinical utility.
Plausibility.57
Novelty.37
Impact.58
Basis · grounding2 papers · 1 computed/note
[1]
paper
Immobilized AMPs can screen for surface-active peptides not susceptible to efflux pumps; AMPs acting intracellularly are susceptible to active efflux.
doi: 10.1177/0022034516679973
[2]
sequenceN-terminal FFSLFK segment is hydrophobic and could serve as a tethering anchor while the cationic C-terminal tail remains free for membrane interaction.
[3]
paper
Beta-defensin-derived cationic antimicrobial peptides show potent killing against Gram-negative and Gram-positive bacteria.
doi: 10.1186/s12866-018-1190-z
openupdated 2026-06-05

Do cancer cells have a surface property that attracts this peptide and makes them more vulnerable than normal cells?

Cancer cells rearrange their outer membrane in a way that makes it more negatively charged than healthy cells. If this peptide sticks preferentially to that altered surface and kills those cells, it could offer a new type of cancer-fighting compound that causes less collateral damage to healthy tissue.

The hypothesis
pep-05597 preferentially kills cancer cells over normal somatic cells because its high net positive charge exploits the exposed phosphatidylserine and anionic lipid composition of cancer cell outer membranes, while normal cells with zwitterionic outer leaflets are less susceptible.
Why it’s plausible
The literature chunk from 10.1177/0022034516679973 explicitly states that cancer cells lose membrane asymmetry, making their outer monolayer more negatively charged, which may explain why some cationic peptides are selectively toxic to tumor cells. pep-05597 carries an exceptionally high positive charge, particularly in its C-terminal cluster (KEKKIRLKKRKKW), which mirrors the charge profile of cationic AMPs noted to exploit this cancer-cell membrane property. The peptide is a designed artificial beta-defensin (10.1042/BJ20082242) incorporating hallmark features selected from natural peptides, which may have amplified this selectivity.
Why it matters
Demonstrating selective cancer cell killing would open a therapeutic avenue entirely distinct from the antibacterial annotation, potentially positioning pep-05597 as a lead for oncolytic peptide development without the off-target toxicity to normal tissues.
Plausibility.63
Novelty.20
Impact.65
Basis · grounding2 papers · 1 computed/note
[1]
paper
Cancer cells lose outer membrane lipid asymmetry, making their surface more electronegative; some cationic peptides are selectively active against tumor cells for this reason.
doi: 10.1177/0022034516679973
[2]
sequenceNet positive charge concentrated in C-terminal KEKKIRLKKRKKW motif plus distributed K/R residues throughout the 57-aa sequence.
[3]
paper
This designed artificial beta-defensin was built from natural peptide primary structures and shows hallmark features of natural defensins, possibly including charge-driven selectivity properties.
doi: 10.1042/bj20082242
openupdated 2026-06-05

Could a small amount of this peptide stop the fungus Candida from forming the protective layers that make it so hard to clear?

Candida biofilms, the sticky communities the fungus forms on catheters and tissues, are notoriously resistant to antifungal drugs and cause serious infections in vulnerable patients. If this peptide can interfere with biofilm formation at doses too low to cause broader harm, it could be a useful tool against a problem that current drugs increasingly struggle to solve.

The hypothesis
pep-05597 inhibits biofilm formation by Candida albicans at sub-MIC concentrations by disrupting the electrostatic interaction between fungal cell wall mannoproteins and the extracellular matrix, independently of its direct membrane-lytic activity against planktonic cells.
Why it’s plausible
Beta-defensins have documented antifungal properties beyond bacteria, and the selectivity axis hit from 10.1007/s00251-001-0412-x notes that single amino acid substitutions in defensins can enable selective interaction with one or more microbial targets. C. albicans biofilms are a critical clinical problem in immunocompromised patients, and mannoproteins on the fungal surface carry strong negative charges that could engage the high-cationic-density C-terminal cluster of pep-05597. At sub-MIC concentrations, charge-driven disruption of mannoprotein-matrix adhesion could impair biofilm without requiring full membrane permeabilization, representing a separate mode of action from planktonic killing.
Why it matters
Anti-biofilm activity against C. albicans would extend the therapeutic relevance of pep-05597 to invasive candidiasis, a disease with rising azole resistance rates, without requiring new structural optimization.
Plausibility.42
Novelty.45
Impact.57
Basis · grounding2 papers · 1 computed/note
[1]
paper
Single amino acid substitutions in defensins may enable selective interaction with one or more microbial targets; cationic charge is correlated with antimicrobial potency.
doi: 10.1007/s00251-001-0412-x
[2]
sequenceHigh net positive charge across the full sequence, especially the C-terminal KEKKIRLKKRKKW cluster, is chemically consistent with disruption of negatively charged fungal mannoprotein-matrix interactions.
[3]
paper
Host-defence peptides can preferentially target pathogens without devastating commensal populations, suggesting selectivity between fungal pathogens and host microbiota is achievable.
doi: 10.1038/s41573-019-0058-8
openupdated 2026-06-05

Could this peptide act as a chemical signal that calls immune cells to a site of injury or infection?

Some natural defensive peptides do double duty, killing microbes and also alerting the immune system to rally reinforcements. If the charged tail of this peptide independently signals immune cells to move in, it could have uses beyond antibiotics, for instance speeding up wound healing or boosting the effectiveness of vaccines.

The hypothesis
The cationic C-terminal region of pep-05597 binds heparan sulfate proteoglycans on host cell surfaces with sufficient affinity to act as a chemokine-like signal that recruits dendritic cells or CCR2-expressing monocytes, independent of any direct antimicrobial effect.
Why it’s plausible
Beta-defensins are well-established chemoattractants for immune cells, a function attributable to polycationic regions that mimic chemokine surface charge and engage glycosaminoglycan receptors. The axis hit from 10.1074/jbc.M709238200 notes that beta-defensin chemoattractant and antimicrobial activities are separable. The pep-05597 sequence contains a C-terminal tail (positions approximately 44-57: KEKKIRLKKRKKW) that is chemically analogous to chemokine heparin-binding domains, which characteristically cluster basic residues. If this region independently docks on heparan sulfate, it would trigger immune cell recruitment even in settings where bacterial targets are absent.
Why it matters
A peptide with separable chemoattractant activity could serve as an immunoadjuvant or wound-healing stimulant, broadening therapeutic utility beyond infection to chronic wounds or vaccine formulations.
Plausibility.47
Novelty.33
Impact.55
Basis · grounding1 paper · 1 computed/note
[1]
paper
Beta-defensin chemoattractant and antimicrobial activities are separable and both are independent of intramolecular disulfide bonds.
doi: 10.1074/jbc.m709238200
[2]
sequenceC-terminal KEKKIRLKKRKKW contains XBBXBX-type motifs (where B is basic) characteristic of heparin-binding domains in chemokines and growth factors.
details expand to inspect
full evidence table1 metrics
metricvaluetool
ranking score 0.7473565340042114 boltz-2
3-letter notation
Phe-Phe-Ser-Leu-Phe-Lys-Ala-Arg-Thr-Leu-Phe-Phe-Lys-Asp-Thr-Cys-Ser-Leu-Glu-Gly-Tyr-Thr-Cys-Arg-Met-Lys-Cys-Asn-Ala-Asp-Glu-His-Ala-Ile-Arg-Tyr-Cys-Thr-Asp-Trp-Thr-Ile-Cys-Cys-Lys-Glu-Lys-Lys-Ile-Arg-Leu-Lys-Lys-Arg-Lys-Lys-Trp
recipeboltz-2 2.2.1
parametervalue
modelboltz-2 2.2.1
weights
hardwarevast_v100_32gb
mlx version
python
random seed1
msa strategynone_monomer
runtime
predicted by
predicted at2026-05-23
citationbibtex
peptidemodel (2026). Beta-defensin 131A antimicrobial peptide (pep-05597, v1). PeptideModel. https://peptidemodel.com/card/pep-05597
@peptide{pep05597,
  sequence = {FFSLFKARTLFFKDTCSLEGYTCRMKCNADEHAIRYCTDWTICCKEKKIRLKKRKKW},
  target   = {antimicrobial},
  author   = {peptidemodel},
  year     = {2026},
  status   = {bioassayed}
}
related peptides 5 by signal overlap
references 3 papers
[2] supporting
[3] supporting
discussion no comments
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