A NOVEL INSECT DEFENSIN FROM THE ANT FORMICA-RUFA

By combination of size exclusion and reversed-phase chromatography, we have isolated a novel member of insect defensin-type antimicrobial pe ptides from the entire bodies of bacteria-challenged Formica rufa (hym enoptera, formicidae). The molecular mass of the purified peptide was estimated to be 4120.42 by matrix-assisted laser desorption/ionization -time of flight/mass spectrometry. Sequence analysis revealed that thi s peptide consisted of 40 amino acid residues with six cysteines engag ed in the formation of three intramolecular disulfide bridges. This pe ptide is unique among the arthropod defensins in terms of the presence of asparatic acid and alanine at position 33 and as C-terminal residu e, respectively. In addition, this novel defensin from Formica rufa ha s the particularity to have no C-terminal extension in contrast to tho se reported for other hymenoptera defensins. ((C) Societe francaise de biochimie et biologie moleculaire/Elsevier, Paris).