Antimicrobial peptides with atypical structural features from the skin of the Japanese brown frog Rana japonica

Todd Isaacson, Ana Maria Soto, Shawichi Iwamuro, Floyd C. Knoop, J. Michael Conlon

Research output: Contribution to journalArticlepeer-review

78 Citations (Scopus)


Japonicin-1 (FFPIGVFCKIFKTC) and japonicin-2 (FGLPMLSILPKALCILLKRKC), two peptides with differential growth-inhibitory activity against the Gram-negative bacterium, Escherichia coli and the Gram-positive bacterium Staphylococcus aureus, were isolated from an extract of the skin of the Japanese brown frog Rana japonica. Both peptides show little amino acid sequence similarity to previously characterized antimicrobial peptides isolated from the skins of Ranid frogs. Circular dichroism studies, however, demonstrate that japonicin-2 adopts an α-helical conformation in 50% trifluoroethanol in common with many other cationic antimicrobial peptides synthesized in amphibian skin. Peptides belonging to the brevinin-1, brevinin-2, and tigerinin families, previously identified in the skins of Asian Ranid frogs, were not detected but a temporin-related peptide (ILPLVGNLLNDLL.NH2; temporin-1Ja), that atypically bears no net positive charge, was isolated from the extract. The minimum inhibitory concentrations (MICs) of the peptides against E. coli were japonicin-1, 30 μM; japonicin-2, 12 μM; and temporin-1Ja > 100 μM. The MICs against S. aureus were japonicin-1, > 100 μM; japonicin-2, 20 μM; and temporin-1Ja, > 100 μM.

Original languageEnglish
Pages (from-to)419-425
Number of pages7
Issue number3
Publication statusPublished - 2002
Externally publishedYes


  • Amphibian skin
  • Antimicrobial peptide
  • Japonicin
  • Rana
  • Temporin

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • Endocrinology
  • Cellular and Molecular Neuroscience


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