1.C.117 The Antibacterial Peptide Lebocin (Lebocin) Family
Insects produce antimicrobial peptides (AMPs) in response to microbial infections. Most AMPs are synthesized as inactive precursors/pro-proteins and require proteolytic processing to generate small active peptides. Two lebocin-related proteins (Leb-B and Leb-C) are from the tobacco hornworm, Manduca sexta. The mRNA levels of Leb-B and Leb-C increased significantly in larval fat body and hemocytes after injection of Escherichia coli, Micrococcus luteus and Saccharomyces cerevisiae. Western blotting using rabbit polyclonal antibody to Leb-B showed accumulation of large protein(s) and small peptide(s) in larval hemolymph after microbial injection. This result and the presence of RXXR motifs in the deduced amino acid sequences led to the postulate that Leb-B/C may be inactive precursors that are processed in larval hemolymph to generate short active peptides. Active antibacterial M. sexta lebocin peptides were located at the N-termini of Leb-B/C, which is different from Bombyx mori lebocins 1-4 where the active parts are located close to the C-termini. Synthetic Leb-B(22-48) peptide not only had higher antibacterial activity but also caused agglutination of E. coli cells (Rao et al. 2012).