title: Leptodactylus ocellatus (Amphibia): mechanism of defense in the skin and molecular phylogenetic relationships.
abstract: Amphibian antimicrobial peptides have been known for many decades and several of them have already been isolated. However, the number of species investigated is still small. Herein, we report on the skin secretions of Leptodactylus ocellatus, which were extracted by mild electrical stimulation and its semi-preparative reverse-phase chromatography was resolved in more than 30 fractions. Among these fractions, two novel antimicrobial peptides were isolated and their amino acid sequences determined by de novo sequencing. The ocellatins-5 and -6 (21 and 22 amino acid residues, respectively) are amidated at the C-terminus. Ocellatins inhibited the growth of reference strains of both Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus) with minimal inhibition concentration values in the range of 32-128 microg/mL. The amino acid sequence of the peptides shows structural similarity with members of the antimicrobial peptides found in the skin secretion of other leptodactylid frogs. This observation is consistent with the hypothesis that many frog skin antimicrobial peptides are related evolutionarily, having arisen from multiple duplications of an ancestral gene that existed before the radiation of the different species.
authors.affiliation: Núcleo de Pesquisa em Biodiversidade e Biotecnologia, Campus Ministro Reis Velloso (CMRV), Universidade Federal do Piauí-UFPI, Parnaíba, Piauí, PI, Brazil. jrsaleite@gmail.com
authors.forename: João Manoel Almeida
authors.initials: JM
authors.lastname: Leite
authors.forename: Luciano Paulino
authors.initials: LP
authors.lastname: Silva
authors.forename: Roberta Rocha
authors.initials: RR
authors.lastname: Silva-Leite
authors.forename: Ana Stella
authors.initials: AS
authors.lastname: Ferrari
authors.forename: Sergio Eustáquio
authors.initials: SE
authors.lastname: Noronha
authors.forename: Helio Ricardo
authors.initials: HR
authors.lastname: Silva
authors.forename: Carlos
authors.initials: C
authors.lastname: Bloch
authors.forename: José Roberto de Souza de Almeida
authors.initials: JR
authors.lastname: Leite
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D001938:Brazil; D017753:Ecosystem; D013058:Mass Spectrometry; D008826:Microbial Sensitivity Tests; D010802:Phylogeny; D011898:Ranidae / Q000235:genetics / Q000502:physiology*; D020539:Sequence Analysis, Protein; D012867:Skin / Q000378:metabolism*
chemical_list: D023181:Antimicrobial Cationic Peptides