Purification and characterization of three isoforms of chrysophsin, a novel antimicrobial peptide in the gills of the red sea bream, Chrysophrys major

Authors


N. Iijima, Laboratory of Molecular Cell Biology, Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashihiroshima 739-8528, Japan. Fax: + 81 824 22 7059, Tel.: + 81 824 24 7949, E-mail: noriiij@jpc.hiroshima-u.ac.jp

Abstract

We report here the isolation of three isoforms of a novel C-terminally amidated peptide from the gills of red sea bream, Chrysophrys (Pagrus) major. Peptide sequences were determined by a combination of Edman degradation, MS and HPLC analysis of native and synthetic peptides. Three peptides, named chrysophsin-1, chrysophsin-2, and chrysophsin-3, consist of 25, 25, and 20 amino acids, respectively, and are highly cationic, containing an unusual C-terminal RRRH sequence. The α-helical structures of the three chrysophsin peptides were predicted from their secondary structures and were confirmed by CD spectroscopy. The synthetic peptides displayed broad-spectrum bactericidal activity against Gram-negative and Gram-positive bacteria including Escherichia coli, Bacillus subtilis, and fish and crustacean pathogens. The three peptides were also hemolytic. Immunohistochemical analysis showed that chrysophsins were localized in certain epithelial cells lining the surface of secondary lamellae and eosinophilic granule cell-like cells at the base of the secondary lamellae in red sea bream gills. Their broad ranging bactericidal activities, combined with their localization in certain cells and eosinophilic granule cell-like cells in the gills, suggest that chrysophsins play a significant role in the innate defense system of red sea bream gills.

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