Conformation-dependent antibacterial activity of the naturally occurring human peptide LL-37

Jan Johansson, Gudmundur H. Gudmundsson, Martín E. Rottenberg, Kurt D. Berndt, Birgitta Agerberth*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

487 Citations (Scopus)


The influence of ion composition, pH, and peptide concentration on the conformation and activity of the 37-residue human antibacterial peptide LL- 37 has been studied. At micromolar concentration in water, LL-37 exhibits a circular dichroism spectrum consistent with a disordered structure. The addition of 15 mM HCO3/-, SO4/2-, or CF3CO2/- causes the peptide to adopt a helical structure, with approximately equal efficiency, while 160 mM Cl- is less efficient. A cooperative transition from disordered to helical structure is observed as the peptide concentration is increased, consistent with formation of an oligomer. The extent of α-helicity correlates with the antibacterial activity of LL-37 against both Gram-positive and Gram-negative bacteria. Two homologous peptides, FF-33 and SK-29, containing 4 and 8 residue deletions at the N terminus, respectively, require higher concentrations of anions for helix formation and are less active than LL-37 against Escherichia coli D21. Below pH 5, the helical content of LL-37 gradually decreases, and at pH 2 it is entirely disordered. In contrast, the helical structure is retained at pH over 13. The minimal inhibitory concentration of LL-37 against E. coli is 5 μM, and at 13-25 μM the peptide is cytotoxic against several eukaryotic cells. In solutions containing the ion compositions of plasma, intracellular fluid, or interstitial fluid, LL- 37 is helical, and hence it could pose a danger to human cells upon release. However, in the presence of human serum, the antibacterial and the cytotoxic activities of LL-37 are inhibited.

Original languageEnglish
Pages (from-to)3718-3724
Number of pages7
JournalJournal of Biological Chemistry
Issue number6
Publication statusPublished - 6 Feb 1998


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