Acaloleptins A: Inducible antibacterial peptides from larvae sf the beetle, Acalolepta luxuriosa

We purified and characterized three structurally related antibacterial pept ides with a molecular mass of 8 kDa (acaloleptins A1, A2, and A3) from the hemolymph of immunized larvae of the Udo longicorn beetle, Acalolepta luxur iosa, These peptides have the same 6 N-terminal amino acid residues and sho w potent antibacterial activity against some Gram-negative bacteria. The th ree peptides are thought to be isoforms, Reverse phase HPLC analysis of the hemolymph of immunized and naive larvae showed that acaloleptins A1, A2, a nd A3 were inducible and suggested that all three peptides were produced in a single insect. We determined the complete amino acid sequence of acalole ptin A1. Acaloleptin A1 consists of 71 amino acid residues and shares signi ficant sequence similarity with coleoptericin and holotricin 2, which were isolated from other coleopteran insects. Furthermore, the 29 C-terminal res idues of acaloleptin A1 had 40% identity with the 30 C-terminal residues of hymenoptaecin found in honeybees. (C) 1999 Wiley-Liss, Inc.