A novel antimicrobial peptide from the loach, Misgurnus anguillicaudatus

A novel antimicrobial peptide, named misgurin, was isolated and characterized from the leach (mudfish), Misgurnus anguillicaudatus. The 21-amino-acid peptide with a molecular mass of 2502 Da was purified to homogeneity using a heparin-affinity column and C18 reverse-phase and gel-permeation highperformance liquid chromatography. The complete amino acid sequence of misgurin, which was determined by an automated amino acid sequencer, was Arg-Gln-Arg-Val-Glu-Glu-Leu-Ser-Lys-Phe-Ser-Lys-Lys-Gly-Ala-Ala-Ala-Arg-Arg-Arg-Lys. Misgurin is a strongly basic peptide which has 5 arginine and 4 lysine residues, Comparison of the amino acid sequence with those of other known antimicrobial peptides revealed that misgurin was a novel antimicrobial peptide. Misgurin showed a strong antimicrobial activity in vitro against a broad spectrum of microorganisms without significant hemolytic activity and was about 6 times more potent than magainin 2. Scanning electron microscopy confirmed that the peptide caused damage to the cell membrane by a pore-forming mechanism similar to that of magainin 2. This damage occurred at the minimal inhibition concentration (MIC), but at higher concentration than MIC it lysed the cell. (C) 1997 Federation of European Biochemical Societies.