Identification Of Two New Antibacterial Peptides, Muscin And Domesticn, In Musca Domestica

Based on the Digital Gene Expression Profiling(DGE) and bioinformatics analysis, two potential antimicrobial peptide genes, which named muscin and domesticin, were identified from the housefly(Musca domestica) transcriptome. Quantitative real-time PCR was employed to investigate the tissue distribution of muscin and domesticin m RNA and temporal expression in housefly larvae challenged with bacteria. Anti-microbial and hemolytic activities of the synthetic peptides were tested.The full-length c DNA of muscin was 379 nt, with an open reading frame of 153 nt encoding a peptide of 50 amino acid residues. The deduced peptide contains a putative signal peptide of 25 amino acids. The deduced mature peptide was rich in hydrophobic and positively charged amino acid residues with a theoretical p I of 9.39. Result of q RT-PCR showed that muscin mainly found in hemocyte and fat body. After challenged by bacteria, the expression level of muscin m RNA was up-regulated and reached the maximum level at 6 h. Anti-microbial assays and hemolytic test displayed that Muscin had broad-spectrum bacteriostatic activities and a low hemolytic activity, with the strongest inhibitory effect for Gram-positive bacteria. Disulfide bond structure was one of the important structure for bacteriostatic activities.The full-length c DNA of domesticin was 364 nt, with an open reading frame of 198 nt encoding a peptide of 65 amino acid residues. The deduced peptide contains a putative signal peptide of 25 amino acids. The deduced mature peptide was rich in hydrophobic and positively charged amino acid residues with a theoretical p I of 11.0. Domesticin mature peptide mainly consisted of three short β-sheet and random curl. Domesticin with immune factors from Drosophila had homogenous. Result of q RT-PCR showed that Drosophila mainly found in hemocyte. After challenged by bacteria, the expression level of Drosophila m RNA was up-regulated and reached the maximum level at 12 h. Anti-microbial assays and hemolytic test displayed that Domesticin had broad-spectrum bacteriostatic activities and a low hemolytic activity.In brief, this study cloned antimicrobial peptides muscin and domesticin from housefly, which maybe took part in immune defense against bacterial pathogens in housefly. The synthetic peptides had broad-spectrum bacteriostatic activities, and had medicinal potential.