FK-13
The 13-residue FKRIVQRIKDFLR central fragment of LL-37 — the smallest LL-37 fragment that retains broad-spectrum antimicrobial activity while losing much of the parent peptide's cytotoxicity toward mammalian cells. Research-only; no clinical development program.
A 13-residue peptide corresponding to LL-37 residues 17–29 (Phe-Lys-Arg-Ile-Val-Gln-Arg-Ile-Lys-Asp-Phe-Leu-Arg). Characterized as a minimal fragment retaining the core antimicrobial activity of the parent cathelicidin LL-37 while substantially reducing cytotoxicity toward host cells. Widely used as a research tool for dissecting the structure-activity relationship of LL-37 and as a template for developing LL-37-derived antimicrobial peptide therapeutics. Not in clinical development as a therapeutic; not FDA-approved.
Mechanism of action
Forms amphipathic α-helical conformation on membrane contact, with cationic residues (arginines and lysines) binding negatively charged phospholipid headgroups of bacterial membranes and hydrophobic residues partitioning into the lipid bilayer. Causes membrane disruption at high concentrations and likely secondary effects on intracellular targets. The central fragment retains this membrane-targeting mechanism of the parent LL-37 while lacking the N-terminal and C-terminal regions that contribute to LL-37's cytotoxicity on mammalian cells; this shifts the therapeutic index toward bacterial selectivity. Also retains chemotactic activity on neutrophils and monocytes.
Primary uses
- Antimicrobial peptide research (in vitro and in vivo microbiology)
- LL-37 structure-activity research
- Template for AMP drug discovery
Typical dosing
⚠ No human dosing established. Any human use would be entirely unregulated and unsupported by any clinical evidence.
Regulatory status
Not FDA-approved. Not in any registered clinical trial. Research peptide only, available from peptide-synthesis vendors.
References
- [pubmed] Li X, et al. "Solution structures of human LL-37 fragments and NMR-based identification of a minimal membrane-targeting antimicrobial and anticancer region." J Am Chem Soc, 2006;128:5776-5785.
- [pubmed] Wang G. "Structures of human host defense cathelicidin LL-37 and its smallest antimicrobial peptide KR-12 in lipid micelles." J Biol Chem, 2008;283:32637-32643.
- [review] Kościuczuk EM, et al. "Cathelicidins: family of antimicrobial peptides. A review." Mol Biol Rep, 2012;39:10957-10970.
Related peptides
This entry is for educational purposes only and does not constitute medical advice. Dosing information reflects published regulatory or research data and is not a recommendation. Many compounds described here are not approved for human use in the United States. Consult a licensed medical professional before considering any peptide therapy.