ISOLATION AND CHARACTERIZATION OF A NEW MEMBER OF THE INSECT DEFENSINFAMILY FROM A BEETLE, ALLOMYRINA-DICHOTOMA

A new family member of insect defensin, an antibacterial peptide, has been isolated from larvae of a beetle, Allomyrina dichotoma. The pepti de consisted of 43 amino acids and 6 cystein residues were conserved i n the same position as that of other insect defensins. The new defensi n was found to be inducible by bacterial injection. Analysis of the an tibacterial spectrum of A. dichotoma defensin indicated that this pept ide showed antibacterial activity against Gram-positive bacteria like Staphylococcus aureus and Bacillus subtilis but not against Gramnegati ve bacteria like Escherichia coli and Pseudomonas aeruginosa, indicati ng a typical spectrum of the insect defensin family. In addition, A, d ichotoma defensin also exhibited antibacterial activity against methic illin-resistant S. aureus (MRSA) isolated from a patient. (C) 1996 Aca demic Press, Inc.