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Cathelicidin Same as LL-37: Species and Sequence Comparison
The following table clarifies why 'cathelicidin' alone is insufficient for research peptide specifications. Sequence and bioactivity differ across species despite conserved precursor structure. | Species | Precursor Protein | Active Fragment | Amino Acid Lengt
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- The following table clarifies why 'cathelicidin' alone is insufficient for research peptide specifications. Sequence and bioactivity differ across species despite conserved precursor structure.
- | Species | Precursor Protein | Active Fragment | Amino Acid Length | Sequence Homology to Human LL-37 | Primary Antimicrobial Mechanism | Bottom Line ||—|—|—|—|—|—|| Human | hCAP-18 | LL-37 | 37 | 100% (reference sequence) | Membrane disruption + FPR2 signaling | The standard for translational research; human-specific receptor interactions || Mouse | mCRAMP precursor | CRAMP | 34 | ~60% | Membrane disruption, weaker FPR2 binding | Not a direct functional equivalent; mouse models require validation for human translation || Bovine | Bac5/Bac7 precursor | BMAP-27, BMAP-28, BMAP-34 | 27–34 | ~40% | Intracellular RNA/DNA binding | Mechanistically distinct; used in agricultural antimicrobial research, not human immunology || Porcine | Protegrin precursor | PR-39, Prophenin | 39–42 | ~35% | Membrane disruption + angiogenesis inhibition | Longer peptide with additional C-terminal residues; different receptor profile |
- Cross-species studies attempting to model human LL-37 function using mouse CRAMP encounter two major limitations: sequence divergence and receptor binding differences. Human LL-37 contains the highly conserved FKRIVQRIKDFLR motif responsible for FPR2 binding and chemotactic signaling. Mouse CRAMP has a FKRLKKIGKLKRW sequence in the equivalent region, altering both hydrophobicity and charge distribution. This changes receptor selectivity: CRAMP activates mouse FPR2 ortholog but with 10× lower potency, and it does not activate human FPR2 at physiologically relevant concentrations (<10 µM). Translational conclusions drawn from mouse models require validation with human LL-37 peptide in human cell assays before clinical inference is justified.
- The reason cathelicidin same as LL-37 terminology persists in literature is historical. Early papers used 'cathelicidin' generically before species-specific sequences were fully characterized. Modern peptide synthesis standards require exact sequence specification. When ordering research peptides, specifying 'human LL-37' or providing the explicit 37-amino-acid sequence eliminates ambiguity. Real Peptides synthesizes human LL-37 to the published canonical sequence (UniProt ID P49913 residues 134–170), verified by mass spectrometry at every production batch to confirm sequence fidelity and rule out truncation or substitution errors that alter bioactivity.