title: Antimicrobial peptides with atypical structural features from the skin of the Japanese brown frog Rana japonica.
abstract: 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 alpha-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.NH(2); 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 microM; japonicin-2, 12 microM; and temporin-1Ja > 100 microM. The MICs against S. aureus were japonicin-1, > 100 microM; japonicin-2, 20 microM; and temporin-1Ja, > 100 microM.
authors.affiliation: Regulatory Peptide Center, Department of Biomedical Sciences, Creighton University Medical School, Omaha, NE 68178, USA.
authors.forename: Todd
authors.initials: T
authors.lastname: Isaacson
authors.forename: AnaMaria
authors.initials: A
authors.lastname: Soto
authors.forename: Shawichi
authors.initials: S
authors.lastname: Iwamuro
authors.forename: Floyd C
authors.initials: FC
authors.lastname: Knoop
authors.forename: J Michael
authors.initials: JM
authors.lastname: Conlon
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides; D002942:Circular Dichroism; D004926:Escherichia coli / Q000187:drug effects*; D007564:Japan; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D011487:Protein Conformation; D011506:Proteins / Q000302:isolation & purification / Q000494:pharmacology; D011898:Ranidae; D017386:Sequence Homology, Amino Acid; D012867:Skin / Q000737:chemistry*; D013211:Staphylococcus aureus / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D010455:Peptides; D011506:Proteins; C451505:japonicin 1; C451506:japonicin 2; C104501:temporin