PARASIN-I, AN ANTIMICROBIAL PEPTIDE DERIVED FROM HISTONE H2A IN THE CATFISH, PARASILURUS-ASOTUS

In response to epidermal injury, Pavasilurus asotus, a catfish, secret ed a strong antimicrobial peptide into the epithelial mucosal layer. T he molecular mass of the antimicrobial peptide, named parasin I, was 2 000.4 Die, as determined by matrix-associated laser desorption ionizat ion mass spectrometry. The complete amino acid sequence of parasin I, which was determined by automated Edman degradation, was y-Gly-Lys-Val -Arg-Ala-Lys-Ala-Lys-Thr-Arg-Ser-Ser. Eighteen of the 19 residues ia p arasin I sere identical to the N-terminal of buforin I, ct 39-residue antimicrobial peptide derived from the N-terminal of toad histone H2A [Kim et al, (1996) Biochem. Biophys. Res. Commun. 229, 381-387], which implies that parasin I was cleaved off from the N-terminal of catfish histone H2A, Parasin I showed strong antimicrobial activity, about 12 -100 times more potent than magainin 2, against a wide spectrum of mic roorganisms, without any hemolytic activity, Circular dichroism spectr a of parasin I indicated a structural content of 11% alpha-helix, 33% beta-sheet, and 56% random coils. The beta-sheet axial projection diag ram of parasin I showed an amphipathic structure. Our results indicate that the catfish may produce parasin I from its histone H2A by a spec ific protease upon injury to protect against invasion by microorganism s. (C) 1998 Federation of European Biochemical Societies.