title: Oncorhyncin III: a potent antimicrobial peptide derived from the non-histone chromosomal protein H6 of rainbow trout, Oncorhynchus mykiss.
abstract: The partial N-terminal amino acid sequence of the antimicrobial peptide reported in the present paper has been submitted to the TrEMBL database under the accession number P83338. A 6.7 kDa antimicrobial peptide was isolated from trout skin secretions using acid extraction followed by cation-exchange chromatography, (t)C(18) solid-phase extraction, and C(18) reversed-phase HPLC. The molecular mass of this peptide, which is tentatively named oncorhyncin III, is 6671 Da, as determined by matrix-assisted laser-desorption ionization MS. N-terminal amino acid sequencing revealed that the first 13 residues of oncorhyncin III are identical with those of the non-histone chromosomal protein H6 from rainbow trout. Hence these data combined with the MS results indicate that oncorhyncin III is likely to be a cleavage product of the non-histone chromosomal protein H6 (residues 1-66) and that it probably contains two methylated residues or one double methylation. The purified peptide exhibits potent antibacterial activity against both Gram-positive and Gram-negative bacteria, with minimal inhibitory concentrations in the submicromolar range. The peptide is sensitive to NaCl, and displays no haemolytic activity towards trout erythrocytes at concentrations below 1 microM. Scanning electron microscopy revealed that oncorhyncin III does not cause direct disruption of bacterial cells. Reconstitution of the peptide in planar lipid bilayers strongly disturbs the membranes, but does not induce the formation of stable ion channels. Taken together, these results support the hypothesis that oncorhyncin III plays a role in mucosal innate host defence.
authors.affiliation: Gatty Marine Laboratory, School of Biology, University of St Andrews, Fife KY16 8LB, Scotland, UK.
authors.forename: Jorge M O
authors.initials: JM
authors.lastname: Fernandes
authors.forename: Nathalie
authors.initials: N
authors.lastname: Saint
authors.forename: Graham D
authors.initials: GD
authors.lastname: Kemp
authors.forename: Valerie J
authors.initials: VJ
authors.lastname: Smith
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D004912:Erythrocytes / Q000187:drug effects; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000648:ultrastructure; D006094:Gram-Positive Bacteria / Q000187:drug effects* / Q000648:ultrastructure; D006461:Hemolysis / Q000187:drug effects; D007473:Ion Channels / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008745:Methylation; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009113:Muramidase / Q000378:metabolism; D017686:Oncorhynchus mykiss; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride / Q000494:pharmacology; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D002868:Chromosomal Proteins, Non-Histone; D007473:Ion Channels; D008051:Lipid Bilayers; C476384:Oncorhyncin III; D012965:Sodium Chloride; D009113:Muramidase