Ranatuerin 1T: An antimicrobial peptide isolated from the skin of the frog, Rana temporaria

A peptide, termed ranatuerin 1T, with growth-inhibiting activity toward Staphylococcus aureus, was isolated from an extract of the skin of the European brown frog, Rana temporaria. The primary structure of the peptide was established as: GLLSGLKKVG¹⁰ KHVAKNVAVS²⁰LMDSLKCKIS³⁰GDC. In common with other anti-microbial peptides from Ranid frogs, (e.g., ranalexin, ranatuerins, gaegurins, brevinins, esculetins, rugosins), ranatuerin IT contains an intramolecular disulfide bridge forming a heptapeptide ring but there is little structural similarity outside this cyclic region. The minimum inhibitory concentration (MIC) of ranatuerin 1T was 120 μM against the Gram- positive bacterium S, aureus and 40 μM against the Gram-negative bacterium Escherichia coli, but the peptide was not active against the yeast Candida albicans.