Pleurain-a1-thel

Most amphibians belonging to Rhacophoridae have an arboreal life. A large amount of bioactive peptides have been identified from amphibian skin, but none from amphibians belonging to Rhacophoridae have been reported to date. A tachykinin-like peptide, tachykinin-Thel, was purified and characterized from skin secretions of the tree frog, Theloderma kwangsiensis. Its primary structure was determined as KPSPDRFYGLM-NH2 by Edman degradation and mass spectrometry analysis. cDNA sequence encoding the precursor of tachykinin-Thel was cloned from the skin cDNA library. Tachykinin-Thel induced the contraction of isolated ileum smooth muscle in a dose-dependent manner. The current work reported a bioactive peptide, tachykinin-Thel, from Rhacophoridae amphibians and confirmed the presence of tachykinin-like peptide in the skin of the tree frog, which may facilitate their arboreal life.

While conducting experiments to investigate antimicrobial peptides of amphibians living in the Yunnan-Guizhou region of southwest China, a new family of antimicrobial peptides was identified from skin secretions of the Yunnan frog, Rana pleuraden. Members of the new peptide family named pleurain-As are composed of 26 amino acids with a unique N-terminal sequence (SIIT) and a disulfide-bridged heptapeptide sequence (CRLYNTC). By BLAST search, pleurain-As had no significant similarity to any known peptides. Native and synthetic peptides showed antimicrobial activities against tested microorganisms including Gram-negative and Gram-positive bacteria and fungi. Twenty different cDNAs encoding pleurain-As were cloned from the skin cDNA library of R. pleuraden. The precursors of pleurain-As are composed of 69 amino acid residues including predicted signal peptides, acidic propieces, and cationic mature antimicrobial peptides. The preproregion of pleurain-A precursor comprises a hydrophobic signal peptide of 22 residues followed by an 18 residue acidic propiece which terminates by a typical prohormone processing signal Lys-Arg. The preproregions of precursors are very similar to other amphibian antimicrobial peptide precursors but the mature pleurain-As are different from other antimicrobial peptide families. The remarkable similarity of preproregions of precursors that give rise to very different antimicrobial peptides in distantly related frog species suggests that the corresponding genes form a multigene family originating from a common ancestor. Furthermore, pleurain-As could exert antimicrobial capability against Helicobacter pylori. This is the first report of naturally occurring peptides with anti-H. pylori activity from Rana amphibians.

Intensive studies have demonstrated that there are many antimicrobial peptides in amphibian skins. Three novel antimicrobial peptides were identified from the skin of the frog, Rana shuchinae. They are named shuchins 3-5. Their sequences were determined as KAYSMPRCKGGFRAVMCWL-NH2, KAYSTPRCKGLFRALMCWL-NH2, and KAYSMPRCKYLFRAVLCWL-NH2 by Edman degradation and mass spectrometry analysis, respectively. They are composed of 19 amino acids (aa) with unique sequences. BLAST search indicated that they showed no similarity to any known peptides or proteins. They are a novel family of antimicrobial peptide. These peptides showed antimicrobial activities against all of tested microorganisms including Gram-positive bacteria, Gram-negative bacteria and fungi. The cDNAs encoding precursors of these peptides were cloned from the skin cDNA library of R. shuchinae. The precursors are composed of 64 amino acid residues including predicted signal peptides, acidic spacer peptides, and mature antimicrobial peptides. The current work identified a novel antimicrobial peptide family.