pe
pep-05335 v1 CC-BY-SA-4.0

Lactacin-F LafX anticancer peptide

A peptide studied for its ability to fight cancer cells; experimental, not yet an approved drug.

statuscomputed targetANTICANCER length48 aa refs3
anticancer
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
pTM0.774
avg pLDDT90.8
ranking score0.881
STRUCTURE · PEP-05335 × ANTICANCER
ranking0.881
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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
sequence48 aa
15101520253035404548
NKWGNAVIGAATGATR GVSWCRGFGPWGMTAC ALGGAAIGGYLGYKSN
in the news 27 articles
Hypotheses5 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 peptide that looks promising against cancer cells actually be useless on its own?

If this holds, researchers testing LafX by itself in cancer screens would get false negatives and miss its real potential. The practical upside: any drug built on LafX would need to deliver two peptides together, which changes how it is formulated and tested from day one.

The hypothesis
LafX disrupts cancer cell membranes through a two-peptide synergistic mechanism requiring co-presentation with LafA, rather than acting as an independent membrane-lytic agent, meaning isolated LafX has negligible cytotoxic activity against tumor cells.
Why it’s plausible
The 1994 Journal of Bacteriology study establishes that both lafA and lafX gene products are absolutely required for lactacin F bacteriocin activity. LafX alone was not recovered from N-terminal sequencing of purified active material, suggesting it is present at substoichiometric or latent levels unless partnered with LafA. The anticancer annotation on this card derives from food-peptide reviews that do not report direct LafX-alone cytotoxicity data. Class IIb two-peptide bacteriocins characteristically require both subunits to form a functional transmembrane pore; the same pore-forming logic would apply to cancer membranes if the peptide does exert anticancer activity.
Why it matters
If LafX is inactive alone, any development strategy for anticancer use must focus on a co-formulated LafA/LafX combination, not LafX as a standalone drug. This fundamentally changes the development path and the interpretation of any single-peptide cytotoxicity screen.
Plausibility.87
Novelty.52
Impact.87
Basis · grounding2 papers · 1 computed/note
[1]
paper
Both lafA and lafX gene products are required for lactacin F activity; LafX was not identified by N-terminal biochemical analysis of purified active material.
doi: 10.1128/jb.176.8.2235-2241.1994
[2]
sequenceLafX (48 aa) has a strongly hydrophobic central core (VSWCRGFGPWGMTACALGGAAIGG) consistent with a transmembrane helix that would require a partner peptide to complete a functional pore.
[3]
paper
Anticancer attribution comes from a general review of egg proteins/food peptides, not from a study of LafX in isolation against cancer cells.
doi: 10.3382/ps/pez381
openupdated 2026-06-05

Is there a specific structural feature that locks two peptides together to form a pore, and could we tune it?

If those two glycine positions really are the contact point, scientists could dial the pairing tighter or looser just by swapping in a slightly bulkier amino acid, giving a precise knob to adjust potency without redesigning the whole molecule.

The hypothesis
The repeated GXXXG motif in the C-terminal half of LafX (G34...G38 in the ALGGAAIGG stretch) drives helix-helix dimerization of LafX with LafA, and mutating either glycine to alanine abolishes lactacin F pore activity without affecting individual peptide folding.
Why it’s plausible
The LafX sequence contains a GXXXG-like motif (ALGG at positions 34-37 followed by AAIGG at 38-42), a well-characterized transmembrane helix-helix interaction motif found in pore-forming and receptor proteins. In two-peptide bacteriocins, the GXXXG motif has been shown to mediate the critical helix interface between the two subunits. The literature confirms LafX function is strictly dependent on LafA co-expression, consistent with an obligate heterodimeric helix interaction. No experimental mutagenesis of this motif in LafX has been published.
Why it matters
Confirming that GXXXG drives the LafA-LafX interface would provide a rational engineering handle: substituting G34 or G38 with bulkier residues could be used to tune the LafA-LafX binding affinity and thereby modulate potency in a controlled manner.
Plausibility.50
Novelty.38
Impact.63
Basis · grounding1 paper · 1 computed/note
[1]
sequenceSequence positions 34-42 contain ALGGAAIGG; the GXXXG motif (G34, G38) is a canonical transmembrane helix-helix docking element.
[2]
paper
LafX possesses the molecular features of class II bacteriocins and both subunits are required for activity, consistent with an obligate helix-helix interface between LafA and LafX.
doi: 10.1128/jb.176.8.2235-2241.1994
openupdated 2026-06-05

Can you take the useful half of a two-part peptide, clip it shorter, and chemically staple it so it works on its own?

If it works, this approach could turn a complicated two-ingredient system into a single, well-defined drug, which is far easier and cheaper to manufacture and much simpler to get through regulatory review.

The hypothesis
The glycine-rich hydrophobic core of LafX can be reengineered into a shorter, single-chain stapled peptide (approximately 20 residues) that self-inserts into cancer cell membranes without requiring LafA, by replacing the obligate helix-helix contact face with a hydrocarbon staple.
Why it’s plausible
The central hydrophobic region of LafX (roughly W23 to C33) contains sufficient membrane-inserting residues to act autonomously if the intermolecular LafA-contact face is replaced by an intramolecular structural constraint. Class IIb bacteriocins are known to have segregated functional domains: one subunit contributes target recognition, the other contributes pore lining. If LafX provides the pore-lining helix, a truncated, stapled version mimicking that helix could function without LafA. Stapled helices derived from naturally obligate dimers have been successfully converted to monomeric activity in other bacteriocin systems.
Why it matters
A monomeric, stapled LafX-derived helix would resolve the key developmental obstacle of requiring a two-peptide co-formulation, simplify manufacturing, and produce a well-defined single molecular entity for regulatory purposes.
Plausibility.37
Novelty.58
Impact.63
Basis · grounding2 papers · 1 computed/note
[1]
sequenceResidues 23-33 (WCRGFGPWGMTA) form a hydrophobic, tryptophan-anchored segment that plausibly constitutes an autonomous membrane helix; two flanking cysteines (C21, C33) could serve as staple attachment points.
[2]
paper
LafX possesses the hydrophobic profile and leader sequence of a standalone class II bacteriocin subunit, suggesting the pore-forming core is structurally self-contained even if functionally dependent on LafA.
doi: 10.1128/jb.176.8.2235-2241.1994
[3]
paper
The field is shifting toward shorter designed antimicrobial peptides to reduce synthesis cost, motivating truncation and stapling of longer natural sequences.
doi: 10.1038/srep42994
openupdated 2026-06-05

Does this peptide recognize and attack a membrane fat that cancer cells expose unusually, instead of locking onto a protein?

If the target is that lipid signature, it would help predict which cancer types are most vulnerable and explain why healthy cells might be spared. It would also reveal the most likely way tumors could develop resistance, pointing researchers toward what to watch for early.

The hypothesis
LafX preferentially binds to phosphatidylserine-rich outer leaflet domains characteristic of cancer cell plasma membranes rather than to a protein receptor, with the positively charged N-terminal region (NK) and C-terminal region (YKSN) anchoring to the negatively charged lipid headgroups.
Why it’s plausible
The LafX sequence carries a cationic N-terminus (NK) and a cationic C-terminal cluster (YKSN), flanking a large hydrophobic core. This charge distribution is architecturally similar to cationic anticancer peptides known to exploit the elevated phosphatidylserine exposure on tumor cell surfaces. The annotated target is null, meaning no protein receptor has been identified. The three tryptophan residues (W3, W23, W26) are well-established membrane insertion anchors that position hydrophobic helical segments at the lipid-water interface. A lipid-binding rather than protein-binding mode would also explain why LafX eluded Edman degradation (it may be buried in lipid during purification).
Why it matters
If the target is a lipid composition rather than a protein, LafX selectivity for cancer over normal cells hinges entirely on membrane phosphatidylserine asymmetry, which has direct implications for which cancer types are susceptible and for predicting resistance mechanisms.
Plausibility.45
Novelty.43
Impact.58
Basis · grounding2 papers · 1 computed/note
[1]
sequenceCationic flanking residues NK (N-term) and YKSN (C-term) bracket a 30+ residue hydrophobic core; three tryptophans (W3, W23, W26) are canonical membrane-interfacial anchors.
[2]
paper
Cationic lactoferricin derivatives exploit cancer-cell phosphatidylserine exposure for differential membrane disruption, establishing lipid-targeting as a viable mechanism for peptides of similar charge architecture.
doi: 10.1016/j.bbamem.2015.07.018
[3]
paper
LafX possesses a hydrophobic profile consistent with class II bacteriocins; no protein receptor has been identified for LafX.
doi: 10.1128/jb.176.8.2235-2241.1994
openupdated 2026-06-05

Could a peptide from a common probiotic bacterium help suppress the gut pathogen responsible for C. difficile infections?

C. difficile causes severe, sometimes life-threatening gut infections that are notoriously hard to treat. If the LafA/LafX pair targets these bacteria, it might open a path to a narrow-spectrum gut therapeutic that works with the microbiome rather than wiping it out, and this use case is better supported by existing evidence than the cancer angle.

The hypothesis
LafX retains antimicrobial activity against gut-associated Clostridium species and is therefore a candidate probiotic-adjacent therapeutic to suppress C. difficile overgrowth, independent of any anticancer utility.
Why it’s plausible
Lactacin F is a bacteriocin produced by Lactobacillus acidophilus, a gut commensal. Class IIb two-peptide bacteriocins from LAB typically act on a defined spectrum of Gram-positive bacteria including Clostridiales. LafX is the hydrophobic partner subunit whose pore-forming architecture is similar to nisin and other lantibiotics with demonstrated Clostridium activity. The anticancer annotation is review-based and weakly supported, whereas the bacteriocin activity against Gram-positive pathogens is the original, primary function of lactacin F. The development of microbiome-modulating agents against C. difficile is an active clinical need with no approved peptide drugs.
Why it matters
Repositioning the LafA/LafX system as an anti-Clostridium microbiome therapeutic leverages its native ecological role, and would be a faster path to a concrete indication than the poorly supported anticancer use, especially given the gut-origin of the parent organism.
Plausibility.38
Novelty.50
Impact.55
Basis · grounding1 paper · 2 computed/notes
[1]
paper
Lactacin F is a class II bacteriocin from Lactobacillus acidophilus with defined Gram-positive antimicrobial activity; this is its primary described function.
doi: 10.1128/jb.176.8.2235-2241.1994
[2]
sourceLAB proteolytic systems and bacteriocins are discussed in the context of dairy and gut ecology, establishing relevance to gut-pathogen suppression.
[3]
sourceReview covers bacteriocin-derived peptides from food organisms in the anticancer context, confirming the parent organism is food/gut-derived LAB.
details expand to inspect
full evidence table1 metrics
metricvaluetool
ranking score 0.8813088536262512 boltz-2
3-letter notation
Asn-Lys-Trp-Gly-Asn-Ala-Val-Ile-Gly-Ala-Ala-Thr-Gly-Ala-Thr-Arg-Gly-Val-Ser-Trp-Cys-Arg-Gly-Phe-Gly-Pro-Trp-Gly-Met-Thr-Ala-Cys-Ala-Leu-Gly-Gly-Ala-Ala-Ile-Gly-Gly-Tyr-Leu-Gly-Tyr-Lys-Ser-Asn
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). Lactacin-F LafX anticancer peptide (pep-05335, v1). PeptideModel. https://peptidemodel.com/card/pep-05335
@peptide{pep05335,
  sequence = {NKWGNAVIGAATGATRGVSWCRGFGPWGMTACALGGAAIGGYLGYKSN},
  target   = {anticancer},
  author   = {peptidemodel},
  year     = {2026},
  status   = {computed}
}
related peptides 5 by signal overlap
references 3 papers
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