Peptidomic analysis of the host-defense peptides in skin secretions of the Trinidadian leaf frog Phyllomedusa trinitatis (Phyllomedusidae)

Peptidomic analysis (reversed-phase HPLC combined with MALDI-TOF mass spectrometry and automated Edman degradation) of norepinephrine-stimulated skin secretions from the Trinidadian leaf frog Phyllomedusa trinitatis Mertens 1926 led to the identification and structural characterization of 26 host-defense peptides. On the basis of amino acid sequence similarity, the peptides may be divided into the followings groups: dermaseptins with the conserved N-terminal region GLWSKIK (6 peptides), dermaseptins with the N-terminal region ALWKXXLK (5 peptides), dermaseptins with the conserved N-terminal region GLFKTLIKGAGKMLGHVAK (4 peptides), C-terminally α-amidated and non-amidated forms of the phylloseptins (9 peptides), phyllocaerulein, a peptide (GLVSGLLNSVTGLLGNLAGGGL) with structural similarity to the plasticins, and a putative antioxidant peptide (LTWKIPTRFCGVT). The primary structures of the peptides support the claim based upon morphological criteria that P. trinitatis and Phyllomedusa tarsius are very closely related phylogenetically but are probably not conspecific. Among the phylloseptins, phylloseptin-1.1TR (FLSLIPKIAGGIASLVKNL.NH₂) displayed the most potent antimicrobial activity.