Protein purification and cDNA cloning of a cecropin-like peptide from the larvae of fall webworm ( Hyphantria cunea)

A proteinous antimicrobial substance was purified from the bacteria-challenged larvae of the fall webworm, Hyphantria cunea. It is a cecropin-like antibacterial peptide which exhibits antibacterial activity against Gram-negative and Gram-positive bacteria, and known as Hyphantria cecropin A. The cDNA clones corresponding to this peptide were isolated from a cDNA library constructed from the bacteria-challenged larvae and obtained complete nucleotide sequences. In addition to the Hyphantria cecropin A sequence, we obtained three other cDNAs exhibiting high sequence similarity with Hyphantria cecropin A. We synthesized the C-terminally amidated peptide of 35 residues based on the deduced sequence of the isolated cDNA of Hyphantria cecropin A. The synthetic peptide exhibited strong antibacterial activity against several microbes including medically important bacteria such as Salmonella, Shigella, and fungus such as Candida. A Southern blot experiment using these cloned cDNAs as probes predicted the existence of multiple forms of Hyphantria cecropin genes.