title: Identification of novel peptides from amphibian (Xenopus tropicalis) skin by direct tissue MALDI-MS analysis.
abstract: Twelve novel peptides (Pxt-1 to Pxt-12) were isolated from the skin of Xenopus tropicalis, diploid frogs, using topological MS analysis. Among them, Pxt-8, Pxt-9, and Pxt-10 were the N terminus of Pxt-1, N terminus of Pxt-3 and C terminus of Pxt-11, respectively. The Pxt-3 and Pxt-11 peptides shared significant sequence homologies with magainins 1, -2 and levitide, respectively, which all isolated from X. laevis. Pxt-12 was identical to the X. tropicalis XT-6-like precursor previously isolated by ESI-MS/MS. None of the Pxt peptides contained any Cys, Asp, Tyr or Trp, although Leu and Lys were frequently found as typical frog-skin peptides. RT-PCR analysis confirmed the gene expressions of Pxt-2, Pxt-3, Pxt-4, Pxt-5, Pxt-7 and Pxt-11 in X. tropicalis skin. Several ion peaks corresponding to all identified Pxt peptides were observed with MALDI-MS analysis of X. tropicalis secretory fluids, collected after in vivo stimulation, which suggested that Pxt peptides were definitely secretory molecules. CD studies and Schiffer-Edmundson helical wheel projections suggested that Pxt-5, as well as mastoparan, at least, could form a typical amphiphilic α helix without a phospholipid or a membrane-mimetic solvent (trifluoroethanol). Moreover, Pxt-2 and Pxt-5 showed growth inhibitory effects on both Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). Measurements of dynamic light scattering and the surface tensions of Pxt peptides solutions suggested that both Pxt-2 and Pxt-5 could form associations as micelles and behave like a general surfactant. Moreover, the remarkable foaming properties of Pxt-2 and Pxt-5 were observed, as well as those of the secretory fluids of X. tropicalis.
authors.affiliation: Health Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Osaka, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Shigeri
authors.forename: Akikazu
authors.initials: A
authors.lastname: Yasuda
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Hagihara
authors.forename: Kaito
authors.initials: K
authors.lastname: Nishi
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Watanabe
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Imura
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Inagaki
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Haramoto
authors.forename: Yuzuru
authors.initials: Y
authors.lastname: Ito
authors.forename: Makoto
authors.initials: M
authors.lastname: Asashima
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D054806:Magainins / Q000235:genetics; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D012867:Skin / Q000737:chemistry*; D013045:Species Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014981:Xenopus / Q000235:genetics / Q000378:metabolism*; D029867:Xenopus Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D014982:Xenopus laevis / Q000235:genetics
chemical_list: D023181:Antimicrobial Cationic Peptides; D054806:Magainins; D012333:RNA, Messenger; D029867:Xenopus Proteins; C053301:magainin 2 peptide, Xenopus; C053300:magainin 1 peptide, Xenopus; C055061:levitide
keywords: MALDI-MS; Xenopus tropicalis; amphibian; peptides; surface tension