Isolation and Characterization of a Defensin-Like Peptide (Coprisin) from the Dung Beetle, Copris tripartitus

Abstract

The antibacterial activity of immune-related peptides, identified by a differential gene expression analysis, was investigated to suggest novel antibacterial peptides. A cDNA encoding a defensin-like peptide, Coprisin, was isolated from bacteria-immunized dung beetle, Copris tripartitus , by using differential dot blot hybridization. Northern blot analysis showed that Coprisin mRNA was up-regulated from 4 hours after bacteria injection and its expression level was reached a peak at 16 hours. The deduced amino acid sequence of Coprisin was composed of 80 amino acids with a predicted molecular weight of 8.6 kDa and a pI of 8.7. The amino acid sequence of mature Coprisin was found to be 79.1% and 67.4% identical to those of defensin-like peptides of Anomala cuprea and Allomyrina dichotoma , respectively. We also investigated active sequences of Coprisin by using amino acid modification. The result showed that the 9-mer peptide, LLCIALRKK- NH 2 , exhibited potent antibacterial activities against Escherichia coli and Staphylococcus aureus .