Purification and molecular cloning of cDNA for an inducible antibacterial protein of larvae of a coleopteran insect, Holotrichia diomphalia

Injection of Escherichia coli into larvae of the coleopteran Holotrichia diomphalia results in the appearance of antibacterial activity in the hemolymph. An antibacterial protein, named holotricin 2, was purified from larvae of this insect and characterized. A cDNA clone for holotricin 2 was isolated and its complete sequence was determined. This protein was found to inhibit the growth of Gram-negative bacteria and to consist of 72-amino acid residues with no cysteine residues. Its amino acid sequence is similar to that of coleoptericine, an antibacterial protein isolated from larvae of the coleopteran Zophobas atratus.