1. Cytolytic peptides belonging to the brevinin-1 and brevinin-2 families isolated from the skin of the Japanese brown frog, Rana dybowskii
J Michael Conlon, Jolanta Kolodziejek, Norbert Nowotny, Jérôme Leprince, Hubert Vaudry, Laurent Coquet, Thierry Jouenne, Shawichi Iwamuro Toxicon. 2007 Nov;50(6):746-56. doi: 10.1016/j.toxicon.2007.06.023. Epub 2007 Jul 4.
Peptidomic analysis of an extract of the skins of specimens of Dybowski's brown frog Rana dybowskii Gunther, 1876, collected on Tsushima Island, Japan led to the identification of 10 peptides with differential antibacterial and hemolytic activities. The primary structures of these peptides identified them as belonging to the brevinin-1 (5 peptides) and brevinin-2 (5 peptides) families of antimicrobial peptides. A peptide (FIGPIISALASLFG.NH(2)) with structural similarity to members of the temporin family was also isolated but this component lacked cytolytic activity. Phylogenetic relationships among the Japanese brown frogs (R. dybowskii, R. japonica, R. okinavana, R. ornativentris, R. pirica, R. sakuraii, R. tagoi, and R. tsushimensis) are only incompletely understood. Cladograms based upon maximum parsimony analyses of the brevinin-1 and brevinin-2 amino acid sequences provide strong support for a sister-group relationship between R. dybowskii and R. pirica and somewhat weaker support for a sister-group relationship between R. okinavana and R. tsushimensis. These conclusions are consistent with previous analyses based upon allozyme variations and comparisons of the nucleotide sequences of mitochondrial genes.
2. Antimicrobial peptides of the brevinin-2 family isolated from gastric tissue of the frog, Rana esculenta
Y Wang, F C Knoop, I Remy-Jouet, C Delarue, H Vaudry, J M Conlon Biochem Biophys Res Commun. 1998 Dec 30;253(3):600-3. doi: 10.1006/bbrc.1998.9822.
Four structurally related peptides with potent growth-inhibitory activity towards Escherichia coli were isolated from an extract of the stomach of the European green frog Rana esculenta, and were identified as members of the brevinin-2 family. Two peptides, termed brevinin-2Eg (GIMDTLKNLA10 KTAGKGALQS20 LLNHASCK LS30GQC) and brevinin-2Eh (GIMDTLKNLA10 KTAGKGALQS20 LLNHASCKL S30 KQC) have not been described previously. One peptide is identical to brevinin-2Ec, previously isolated from R. esculenta skin secretions, and one peptide is identical to brevinin-2Ef whose structure has been deduced from a cloned cDNA prepared from a R. esculenta skin cDNA library. The data demonstrate that certain peptides of the brevinin-2 family, like the magainins in the toad, Xenopus laevis, may play an important role in protecting the gastrointestinal tract of Ranid frogs against microbial invasion.
3. A family of brevinin-2 peptides with potent activity against Pseudomonas aeruginosa from the skin of the Hokkaido frog, Rana pirica
J Michael Conlon, et al. Regul Pept. 2004 May 15;118(3):135-41. doi: 10.1016/j.regpep.2003.12.003.
Nine peptides displaying varying degrees of antimicrobial activity were extracted from the skin of the Hokkaido frog, Rana pirica. Five structurally related peptides were identified as members of the brevinin-2 family. These peptides were active against reference strains of Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Enterobacter cloacae, Klebsiella pneumoniae) and Gram-positive (Staphlococcus aureus) bacteria but displayed relatively low hemolytic activity. The most abundant peptide, brevinin-2PRa (680 nmol/g weight of dry skin) showed high potency [minimal inhibitory concentration (MIC) values between 6 and 12 microM] against a range of clinical isolates of P. aeruginosa. In addition, activity was unaffected by NaCl concentrations up to 200 mM. Cladistic analysis based on the primary structures of brevinin-2 peptides supports a close phylogenetic relationship between R. pirica and Japanese mountain brown frog Rana ornativentris. One peptide of the ranatuerin-2 family and one strongly hemolytic peptide of the brevinin-1 family were also isolated from the extract along with two members of the temporin family, temporin-1PRa (ILPILGNLLNGLL.NH(2)) and temporin-1PRb (ILPILGNLLNSLL.NH(2)) that atypically lacked basic amino acid residues and showed only very weak antimicrobial and hemolytic activity.
