Metchnikowin, a novel immune-inducible proline-rich peptide from Drosophila with antibacterial and antifungal properties.

One of the characteristics of the host defense of higher insects is the rapid and transient synthesis of a variety of potent antimicrobial peptides. To date, several distinct inducible antimicrobial peptides or peptide families have been totally or partially characterized. We present here the isolation and characterization of a novel 26-residue proline-rich immune-inducible peptide from Drosophila, which exhibits both antibacterial (Gram-positive) and antifungal activities. Peptide sequencing and cDNA cloning indicate the presense of two isoforms in our Drosophila Oregon strain, which differ by one residue (His compared to Arg) as a consequence of a single nucleotide change. The gene, which maps in position 52A1-2 on the right arm of the second chromosome, is expressed in the fat body after immune challenge. The novel peptide, which we propose to name metchnikowin, is a member of a family of proline-rich peptides, and we discuss the possible evolutionary relationships within this family.