Solution structure of drosomycin, the first inducible antifungal protein from insects

Abstract

Drosomycin is the first antifungal protein characterized recently among the broad family of inducible peptides and proteins produced by insects to respond to bacterial or septic injuries. It is a small protein of 44 amino acid residues extracted from Drosophila melanogaster that exhibits a potent activity against filamentous fungi. Its three-dimensional structure in aqueous solution was determined using ' H 2D NMR. This structure, involving an a-helix and a twisted three-stranded P-sheet, is stabilized by three disulfide bridges. The corresponding Cysteine Stabilized aP (CSaP) motif, which was found in other defense proteins such as the antibacterial insect defensin A, short-and long-chain scorpion toxins, as well as in plant thionins and potent antifungal plant defensins, appears as remarkably persistent along evolution.

Separate jasmonate-dependent and salicylate-dependent defense-response pathways in Arabidopsis are essential for resistance to distinct microbial pathogens

“…In Drosophila, pathogen-induced accumulation of the antifungal peptide drosomycin is controlled by an NF-B͞IB-like signaling pathway, whereas expression of various genes encoding antibacterial peptides is under control of the unknown gene IMD (27,28). Interestingly, drosomycin shows striking sequence and structural homology to the Arabidopsis plant defensin PDF1.2 (29,30). Mutants in the NF-B͞IB-like signaling pathway are highly susceptible to Aspergillus flavus infection but not to E. coli infection, whereas the opposite is true for imd mutants (27,28).…”

Antifungal Proteins

“…Defensins are a diverse group of low-molecularmass cysteine-rich proteins found in mammals, fungi (89), insects (91), and plants (14,16). The insect and mammalian defensins are quite small (3 to 5 kDa) and form voltage-dependent ion channels in plasma membranes (92,93,171). Thionins are also small (3 to 5 kDa) cysteine-rich peptides that are toxic to fungi (171).…”

Eurocin, a New Fungal Defensin

“…Many invertebrate (11) and fungal (12) defensins have a cysteine-stabilized ␣-helix/␤-sheet structure similar to the structure of ␤-defensins from vertebrates. Among others, structures have been solved for Phormia defensin (13), Sarcophaga defensin (14), drosomycin (15), heliomycin (16), terramycin (17), MGD-1 (18), lucifensin (19), and plectasin (20). They all form an ␣-helix and two anti-parallel ␤-strands (␣␤␤-scaffold) with the ␣-helix stabilized by two disulfide bridges to one strand of the ␤-sheet.…”

“…The cDNA clone encoded a putative defensin-like peptide that was named eurocin. The gene encodes 90 amino acids (signal peptide (amino acids (aa) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], propeptide (aa , and defensin peptide (aa 49 -90)). The mature peptide consists of 42 amino acids ( Fig.…”