pe
pep-05476 v1 CC-BY-SA-4.0

ABF-2 antimicrobial peptide

A naturally derived peptide that kills or stops the growth of bacteria and other microbes; used only as a lab research tool.

statuscomputed targetANTIMICROBIAL length60 aa refs3
antibacterialantimicrobial
EARLY ENTRY This candidate is newly indexed — supporting evidence is still being added. Have a paper or data point? Contribute below.
status 2 / 5 · 2 contributors
prediction metrics boltz-2 2.2.1
ipTM0.000
pTM0.460
avg pLDDT62.3
ranking score0.590
STRUCTURE · PEP-05476 × ANTIMICROBIAL
ranking0.590
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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
sequence60 aa
151015202530354045505560
MDIPGLDRAARALCIASCSL QNCATGNCEVREGRKTCVCS RCKDGGNVPLDKLIGIASKF
in the news 6 articles
Hypotheses7 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 a single small change to ABF-2's structure stop it from falling apart before it reaches its target?

ABF-2 has one protein building block that appears to have no partner, which can cause the molecule to clump or get neutralized in wound fluid before doing its job. If swapping or pairing that one piece prevents this, the result could be a more shelf-stable, consistently effective antibiotic that is easier to manufacture, which matters for anyone developing it into a real treatment.

The hypothesis
Replacing the single odd cysteine in ABF-2 (if the seventh cysteine at position 42 lacks a disulfide partner) with a serine, or adding a complementary cysteine to form a fourth disulfide bond, will increase proteolytic stability and antibacterial potency because it resolves a free thiol that may form aberrant intermolecular disulfides under oxidative conditions.
Why it’s plausible
Most plant defensins with the CSalphaBeta scaffold have an even number of cysteines (typically 6 or 8) forming 3 or 4 disulfide bonds. ABF-2 has 7 cysteines (positions 14, 18, 23, 28, 37, 39, 42), leaving one cysteine potentially unpaired. A free thiol in an oxidative environment (e.g., wound fluid) would form disulfide-linked dimers or mixed disulfides with serum albumin, reducing effective monomer concentration and activity. Engineering either a fourth disulfide or removing the unpaired cysteine would improve stability and reproducibility of activity.
Why it matters
Oxidative instability is a practical barrier to AMP clinical translation; a single-residue fix that resolves a free thiol would substantially improve shelf life, activity in biological fluids, and manufacturing consistency without altering the core pharmacophore.
Plausibility.68
Novelty.65
Impact.63
Basis · grounding2 papers · 1 computed/note
[1]
sequenceSeven cysteines at positions 14, 18, 23, 28, 37, 39, 42 - an odd number that implies at least one unpaired thiol under native folding conditions
[2]
paper
Proteolytic stability engineering of AMPs through structural modifications that preserve fold integrity
doi: 10.1021/acs.jmedchem.8b01348
[3]
paper
Rational avoidance of structural liabilities (including reactive thiols) significantly enhances AMP therapeutic potential
doi: 10.1038/s41598-025-06522-8
openupdated 2026-06-05

Could ABF-2, known as an antibacterial, also kill the fungal pathogens that often accompany bacterial infections?

Wound infections frequently involve both bacteria and fungi at the same time, yet most available drugs target only one or the other. If ABF-2 turns out to be active against Candida as well as bacteria, a single compound could address both threats simultaneously, which would be especially valuable in hard-to-treat infections in immunocompromised patients.

The hypothesis
ABF-2 possesses antifungal activity against human-pathogenic Candida species at concentrations comparable to its antibacterial MIC, because its cysteine-rich plant defensin scaffold shares structural homology with antifungal defensins that target fungal membrane sphingolipids.
Why it’s plausible
ABF-2 belongs to the plant defensin (gamma-thionin) superfamily, whose founding members (e.g., Rs-AFP2 from radish, RsD1 from radish) are primarily antifungal and act by binding glucosylceramide in fungal membranes. The card annotates ABF-2 as antibacterial only, but given its structural class this may reflect incomplete characterization rather than genuine selectivity for bacteria over fungi. The cationic, disulfide-stabilized scaffold present here is exactly what is exploited in antifungal defensins. Fungal co-infections with antibiotic-resistant bacteria are a recognized unmet clinical need.
Why it matters
If ABF-2 has dual antibacterial and antifungal potency, it would be a candidate for treating polymicrobial wound infections where both bacterial and fungal pathogens are present, substantially expanding its therapeutic scope beyond current annotations.
Plausibility.53
Novelty.52
Impact.70
Basis · grounding1 paper · 1 computed/note
[1]
sequenceSeven-cysteine motif with spacing pattern consistent with plant defensin CSalphaBeta fold shared by well-characterized antifungal defensins
[2]
paper
Antifungal peptides can be optimized to gain dual antibacterial activity, implying the scaffold classes overlap; the converse repurposing from antibacterial to antifungal is equally plausible
doi: 10.1186/s12866-025-04160-8
openupdated 2026-06-05

Does ABF-2 attack bacteria through two separate mechanisms, making it much harder for bacteria to resist?

When an antibiotic works through a single pathway, bacteria can sometimes evolve a workaround. If ABF-2 simultaneously disrupts the bacterial membrane and blocks cell-wall construction, bacteria would need to develop two independent defenses at the same time, which is far less likely. This could make it a stronger candidate in the fight against drug-resistant infections.

The hypothesis
ABF-2 directly binds to lipid II, the bacterial cell-wall precursor, at its pyrophosphate moiety, acting as a dual mechanism agent that both permeabilizes membranes and blocks peptidoglycan synthesis.
Why it’s plausible
Several cysteine-rich defensins, most notably human defensin HNP-1 and plant defensin MtDef4, have been shown to bind lipid II via cationic residues that contact the pyrophosphate group. ABF-2's sequence contains a REGRK motif (positions 32-36) that is rich in cationic residues clustered in a loop region (after the second cysteine pair), consistent with a lipid II binding geometry. Lipid II binding by defensins confers activity at nanomolar concentrations far below what membrane disruption alone would require, explaining why some defensins have very low MICs.
Why it matters
If ABF-2 binds lipid II, it would join a mechanistically privileged class of AMPs (alongside lantibiotics like nisin) where dual-mechanism action dramatically reduces the probability of resistance emergence, making it a higher-priority development candidate.
Plausibility.40
Novelty.57
Impact.70
Basis · grounding2 papers · 1 computed/note
[1]
sequenceREGRK motif at positions 32-36 forms a cationic cluster within the loop between the second and third cysteine pairs, structurally analogous to lipid II-binding loops in other defensins
[2]
paper
Overview covers diverse AMP mechanisms including cell-wall precursor binding alongside membrane disruption
doi: 10.2174/0929866529666220613102145
[3]
paper
Dual-mechanism AMPs that combine membrane disruption with intracellular targeting or cell-wall synthesis inhibition show reduced resistance emergence rates
doi: 10.1016/j.micres.2024.127822
openupdated 2026-06-05

Could the compact folded shape of ABF-2 be what prevents it from damaging human cell membranes?

A common problem with antibiotic peptides is that they can be toxic to human cells as well as bacteria. If ABF-2's rigidity physically prevents it from inserting deeply into human cell membranes, that structural difference could explain a built-in safety margin. Understanding this would help researchers design safer variants, particularly for topical wound treatments.

The hypothesis
ABF-2 is selectively toxic to bacteria over mammalian cells because its activity depends on the high density of anionic phospholipids in bacterial membranes, and its compact disulfide-stabilized scaffold reduces insertion depth into zwitterionic cholesterol-rich mammalian bilayers.
Why it’s plausible
The sequence carries strong positive charge but also contains hydrophobic clusters (AALCI at 12-16, VPLDK at 48-52, LIGIA at 53-57) that would drive hydrophobic insertion. However, the rigid disulfide-cross-linked CSalphaBeta fold limits the conformational flexibility needed to fully insert into cholesterol-ordered mammalian bilayers, which have a larger hydrophobic thickness. Bacterial membranes lacking cholesterol and enriched in phosphatidylglycerol/cardiolipin would be preferentially attacked. This geometric selectivity is distinct from charge-only models.
Why it matters
Establishing a structural (not merely charge-based) basis for selectivity would guide engineering of ABF-2 analogs with improved therapeutic index, particularly for topical applications in skin infections where mammalian cell toxicity is a key safety concern.
Plausibility.45
Novelty.52
Impact.57
Basis · grounding2 papers · 1 computed/note
[1]
sequenceMultiple hydrophobic clusters alongside cationic residues suggest amphipathic surface; seven cysteines enforce a rigid fold limiting bilayer insertion depth
[2]
paper
Selectivity of AMPs arises from complex interplay of charge, rigidity, and membrane composition rather than charge alone
doi: 10.1021/acschembio.9b00782
[3]
paper
Plant defensin-like peptides can be non-hemolytic and show low mammalian toxicity while retaining antibacterial/antifungal activity
doi: 10.1016/j.bbamem.2019.183092
openupdated 2026-06-05

Could ABF-2 kill bacteria that have already become resistant to our best antibiotics?

MRSA and carbapenem-resistant bacteria are among the most dangerous drug-resistant pathogens globally, responsible for tens of thousands of deaths each year. Because ABF-2 targets bacterial membranes rather than the molecular pathways that existing antibiotics rely on, the tricks bacteria use to resist conventional drugs would likely not protect them here. If confirmed in testing, this could establish a clear path toward clinical development.

The hypothesis
ABF-2 retains antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and carbapenem-resistant Pseudomonas aeruginosa because its membrane-targeting mechanism is orthogonal to the resistance pathways that disable beta-lactam and carbapenem antibiotics.
Why it’s plausible
Resistance to conventional antibiotics arises through target mutation, enzymatic inactivation (beta-lactamases), or efflux pump upregulation. None of these mechanisms directly neutralize a cationic peptide that disrupts membrane integrity. Plant defensins with the same structural scaffold have shown activity against multidrug-resistant organisms in vitro. The sequence of ABF-2 shows no beta-lactam binding domain and no known efflux pump substrate motif, supporting orthogonal activity.
Why it matters
MRSA and carbapenem-resistant Gram-negatives represent critical-priority pathogens by WHO classification; demonstrating ABF-2 activity against these strains would establish a clear clinical development rationale and differentiate it from existing antibiotic classes.
Plausibility.62
Novelty.15
Impact.62
Basis · grounding2 papers · 1 computed/note
[1]
paper
AMPs overcome resistance because their membrane-disruption mechanism is independent of the enzymatic and efflux-based resistance pathways that defeat conventional antibiotics
doi: 10.1016/j.micres.2024.127822
[2]
paper
Cationic AMPs described as active against multidrug-resistant organisms due to mechanistic orthogonality
doi: 10.1038/nbt1267
[3]
sequenceNet-positive charge and cysteine-stabilized fold are the key structural features driving membrane targeting, not a protein binding motif susceptible to target-site mutation
openupdated 2026-06-05

Does ABF-2 work by physically breaking down the bacterial membrane rather than blocking a specific protein?

When an antibiotic works by blocking a specific protein, bacteria can evolve resistance by mutating that protein. If ABF-2 instead kills by physically disrupting the membrane itself, there is no single mutation that would protect bacteria, making resistance far less likely to emerge. Confirming this mechanism would strengthen the case for developing it as a treatment.

The hypothesis
ABF-2 exerts its antibacterial activity primarily by permeabilizing bacterial membranes through electrostatic interaction with anionic lipopolysaccharide and phosphatidylglycerol headgroups rather than by binding a specific intracellular protein target.
Why it’s plausible
The sequence contains several cationic residues (R8, R11, K35, R41, K43, K52, K59) distributed across the 60-mer, giving a net positive charge typical of membrane-active defensins. Plant defensins in the gamma-thionin family, which ABF-2 belongs to, are well documented to disrupt bacterial membrane integrity. The absence of any annotated protein target in the card is consistent with a membrane-lytic rather than receptor-binding mechanism. The seven cysteines (positions 14, 18, 23, 28, 37, 39, 42) forming multiple disulfide bonds create a compact, protease-resistant scaffold ideally suited for sustained membrane contact.
Why it matters
Confirming a membrane-disruption mechanism rather than a protein-target mechanism would explain ABF-2's broad-spectrum activity and its low propensity for resistance development, which directly informs whether resistance can emerge via target mutation.
Plausibility.58
Novelty.12
Impact.55
Basis · grounding2 papers · 1 computed/note
[1]
sequenceSeven cysteines consistent with a CSalphaBeta plant defensin fold; multiple lysine and arginine residues conferring net positive charge for anionic membrane binding
[2]
paper
Overview of AMP structure-function links membrane disruption to cationic character and compact disulfide-stabilized folds
doi: 10.2174/0929866529666220613102145
[3]
paper
Discusses how membrane-targeting AMPs resist the same resistance pathways as protein-targeting antibiotics
doi: 10.1016/j.micres.2024.127822
openupdated 2026-06-05

Could a shorter version of ABF-2 work just as well, costing less to make?

Manufacturing cost is one of the biggest barriers to turning peptide antibiotics into real drugs. If the first stretch of ABF-2 turns out to be dispensable for killing bacteria, researchers could focus on a shorter, cheaper-to-synthesize version. For anyone funding or developing this compound, that could be the difference between a viable product and one that never reaches patients.

The hypothesis
The three-disulfide-bond core of ABF-2 (formed by its seven cysteines) is sufficient for antibacterial activity, and the N-terminal segment MDIPGLDRAARAL (residues 1-13) preceding the first cysteine is dispensable for potency but contributes to solubility and thermal stability.
Why it’s plausible
The first 13 residues of ABF-2 are unusually hydrophobic and contain a proline-glycine turn motif (PGLD at positions 4-7) that is atypical of canonical plant defensin cores, which begin near the first cysteine. In most gamma-thionin defensins, the core CSalphaBeta domain alone retains antimicrobial activity. The N-terminal tail may represent a signal/pro-peptide remnant or a solubility tag that was retained in the mature form. If this tail is dispensable, truncated analogs could be produced at lower cost.
Why it matters
Identifying which portion of the 60-mer is the minimal active core would reduce manufacturing costs (a major barrier cited for AMP therapeutics) and provide a rational starting point for shorter analogs.
Plausibility.38
Novelty.42
Impact.52
Basis · grounding1 paper · 1 computed/note
[1]
sequenceResidues 1-13 (MDIPGLDRAARAL) contain no cysteine and include an unusual hydrophobic-proline motif absent from core defensin templates; the cysteine-rich scaffold begins at position 14
[2]
paper
High cost of manufacturing longer peptides ($100-$600/g) is the single largest barrier to AMP development, motivating minimal-core truncation strategies
doi: 10.1038/nbt1267
details expand to inspect
full evidence table1 metrics
metricvaluetool
ranking score 0.5903340578079224 boltz-2
3-letter notation
Met-Asp-Ile-Pro-Gly-Leu-Asp-Arg-Ala-Ala-Arg-Ala-Leu-Cys-Ile-Ala-Ser-Cys-Ser-Leu-Gln-Asn-Cys-Ala-Thr-Gly-Asn-Cys-Glu-Val-Arg-Glu-Gly-Arg-Lys-Thr-Cys-Val-Cys-Ser-Arg-Cys-Lys-Asp-Gly-Gly-Asn-Val-Pro-Leu-Asp-Lys-Leu-Ile-Gly-Ile-Ala-Ser-Lys-Phe
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). ABF-2 antimicrobial peptide (pep-05476, v1). PeptideModel. https://peptidemodel.com/card/pep-05476
@peptide{pep05476,
  sequence = {MDIPGLDRAARALCIASCSLQNCATGNCEVREGRKTCVCSRCKDGGNVPLDKLIGIASKF},
  target   = {antimicrobial},
  author   = {peptidemodel},
  year     = {2026},
  status   = {computed}
}
related peptides 5 by signal overlap
references 3 papers
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