PURIFICATION AND PARTIAL CHARACTERIZATION OF AN INDUCED ANTIBACTERIALPROTEIN IN THE SILKWORM, BOMBYX-MORI

Injection of live Escherichia coli into larvae of the silkworm, Bombyx mori, induces antibacterial activity in the hemolymph. The major indu ced antibacterial activity was purified in two steps by CM-Sephadex C- 50 and Sephadex G-100 column chromatography. After trypsin treatment, the purified antibacterial protein lost its activity and the antibacte rial activity was found to be partially heat labile. The purified prot ein was a single polypeptide chain of molecular weight 16 kDa. The 20 N-terminal amino acid sequence of the protein was determined and this sequence showed homology with the N-terminal amino acid sequence of ly sozymes reported in other species. The purified protein was found to h ave comparable antibacterial activity against both E. coli and Microco ccus luteus. The purification of antibacterial protein and the antibac terial properties of the purified protein are discussed. (C) 1995 Acad emic Press, Inc.