Enlarged scale chemical synthesis and range of activity of drosocin, an O-glycosylated antibacterial peptide of Drosophila

• Published in: European journal of biochemistry Vol. 238; no. 1; pp. 64 - 69
• Main Authors: Bulet, P, Urge, L, Ohresser, S, Hetru, C, Otvos, L. Jr
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01-05-1996
• Subjects: Amino Acid Sequence; animal physiology; Animals; antibacterial peptide; arthropods; Circular Dichroism; Drosophila; Drosophila - chemistry; entomology; glycopeptide synthesis; Glycopeptides - chemistry; Glycopeptides - metabolism; Glycopeptides - pharmacology; Glycosylation; Hemolysis - drug effects; insect; Isoenzymes - chemical synthesis; Isoenzymes - metabolism; Isoenzymes - pharmacology; Life Sciences; Microbial Sensitivity Tests; Molecular Sequence Data
• ISSN: 0014-2956; 1432-1033; 0014-2956
• DOI: 10.1111/j.1432-1033.1996.0064q.x

Insects respond to a bacterial challenge by rapidly synthesizing a diverse range of antibacterial and antifungal peptides. One of them, drosocin, a 19-residue proline-rich antibacterial peptide, was isolated from Drosophila. This peptide carries a disaccharide moiety attached to a threonine residue in mid-chain position. The present report describes the enlarged-scale chemical synthesis of drosocin, glycosylated with Gal(beta 1 leads to 3)GalNAc(alpha 1 leads to O). We have studied the range of activity of the synthetic glycopeptide, of two truncated glycosylated isoforms, and of the unglycosylated L and D enantiomers. Both isolated and chemically synthesized drosocins carrying the disaccharide display the same antibacterial activity. Using circular dichroic spectroscopy we demonstrated that the O-linked disaccharidic motif did not affect the backbone conformation of drosocin. The antibacterial activity of the synthetic glycopeptide was directed against gram-negative strains with the exception of the gram-positive bacteria Micrococcus luteus. Deletion of the first five N-terminal residues completely abolished the activity of drosocin. As a first approach to the study of the mode of action of drosocin, we have synthesized a non-glycosylated D enantiomer and, using this molecule, we have shown that drosocin may act on the gram-negative bacteria through a stereospecific target.