1. Purification and characterization of antimicrobial peptides from the skin secretions of the carpenter frog Rana virgatipes (Ranidae, Aquarana)
J Michael Conlon, Bency Abraham, Agnes Sonnevend, Thierry Jouenne, Pascal Cosette, Jerome Leprince, Hubert Vaudry, Catherine R Bevier Regul Pept. 2005 Nov;131(1-3):38-45. doi: 10.1016/j.regpep.2005.06.003.
The members of the Aquarana (or Rana catesbeiana species group) form a well-supported monophyletic clade but phylogenetic relationships between species within the group are incompletely understood. Peptides that differentially inhibited the growth of bacteria were purified from electrically stimulated skin secretions of the carpenter frog Rana virgatipes. Structural characterization identified members of the ranatuerin-2 (3 peptides) and temporin (3-peptides) families, previously found in the skins of R. catesbeiana, R. clamitans, R. grylio and R. septentrionalis. Ranalexin, a peptide previously found only in the Aquarana, was isolated together with a variant (FFGLHNLVPSMLCVVRKKC) that lacks the propensity to adopt an alpha-helical conformation and so was devoid of antimicrobial activity. Two C-terminally alpha-amidated peptides belonging to the brevinin-2 family were isolated from the skin secretions that, like an ortholog from R. septentrionalis, lacked the C-terminal cyclic heptapeptide domain associated with members of this family. Ranatuerin-1, previously isolated from R. catesbeiana, R. clamitans and R. grylio but absent from R. septentrionalis, was also not identified in R. virgatipes. Synthetic replicates of temporin-1Va (FLSSIGKILGNLL.NH2), temporin-IVb (FLSIIAKVLGSLF.NH2) and temporin-1Vc (FLPLVTMLLGKLF.NH2) potently inhibited growth of Gram-positive bacteria (including methicillin-resistant Staphylococcus aureus). Temporin-1Va was also active against Gram-negative bacteria and the opportunistic yeast pathogen Candida albicans and had relatively weak hemolytic activity (LD50=120 microM) and may therefore represent a candidate for drug development. Our data support the placement of R. virgatipes in the Aquarana and indicate a closer phylogenetic relationship of R. virgatipes with R. septentrionalis than with R. catesbeiana, R. clamitans and R. grylio.
2. Activities of four frog skin-derived antimicrobial peptides (temporin-1DRa, temporin-1Va and the melittin-related peptides AR-23 and RV-23) against anaerobic bacteria
Edit Urbán, Elisabeth Nagy, Tibor Pál, Agnes Sonnevend, J Michael Conlon Int J Antimicrob Agents. 2007 Mar;29(3):317-21. doi: 10.1016/j.ijantimicag.2006.09.007. Epub 2006 Dec 28.
The activities of two antimicrobial peptides belonging to the temporin family (temporin-1DRa from Rana draytonii and temporin-1Va from Rana virgatipes) and two peptides with structural similarity to the bee venom peptide melittin (AR-23 from Rana tagoi and RV-23 from R. draytonii) were evaluated against a range of reference strains and clinical isolates of anaerobic bacteria. These peptides were selected because they show broad-spectrum growth inhibitory activity against reference strains of several medically important aerobic microorganisms and against clinical isolates of methicillin-resistant Staphylococcus aureus. All peptides showed relatively high potency (minimum inhibitory concentration (MIC)
3. Insulin releasing properties of the temporin family of antimicrobial peptides
Yasser H A Abdel-Wahab, Lamin Marenah, Peter R Flatt, J Michael Conlon Protein Pept Lett. 2007;14(7):702-7. doi: 10.2174/092986607781483822.
Temporin-1Vb, -1Oe, -1DRb, and -1TGb (10(-8) -10(-6)M) produced significant (p<0.05) and concentration-dependent stimulatory effects on insulin secretion from clonal rat BRIN-BD11 cells without increased release of lactate dehydrogenase. Temporin-1Va and temporin-1Vc (10(-8) - 10(-6)M) also stimulated insulin-release but were cytotoxic at 10(-6)M. Temporin-1DRa was without effect. The temporins at 10(-7) M had no effect on intracellular calcium concentrations suggesting that they stimulate insulin release via a K(ATP) channel- independent pathway.
