title: Molecular characterization and expression of a novel big defensin (Sb-BDef1) from ark shell, Scapharca broughtonii.
abstract: Big defensins, endogenous cysteine-rich antimicrobial peptides (AMPs) with antimicrobial activity and immunomodulatory property, play crucial roles in host defense against various microbial pathogens. A novel big defensin (Sb-BDef1) of ark shell Scapharca broughtonii was identified by expressed sequence tag (EST) and RACE techniques. The Sb-BDef1 cDNA contained an open reading frame (ORF) of 336-bp encoding a polypeptide of 111 amino acids with a putative signal peptide of 21 amino acid residues, followed by a putative propeptide of 11 residues and a putative mature peptide of 79 residues. The mature peptide shared the common features of big defensins, including a high hydrophobic residues region (59%) in the N-terminus, a defensin domain in the C-terminus, which perfectly corresponds to the six conserved disulfide-bonded cysteine residues involved in the formation of the internal disulfide bridges (C1-C5, C2-C4 and C3-C6) in all big defensins from mollusk, horseshoe crab and amphioxus. Quantitative real-time PCR analysis revealed that the expression of Sb-BDef1 transcript was detected in all the tissues examined from normal ark shells, and the temporal expression of Sb-BDef1 mRNA was remarkably up-regulated at 8, 16 h in hemocytes, and at 16, 24 h in hepatopancreas after Vibrio anguillarum-challenge, respectively. These results suggested that Sb-BDef1 was a constitutive and inducible acute-phase protein and should be involved in immune response of Gram-negative microbial infection in ark shell S. broughtonii.
authors.affiliation: Key Laboratory of Sustainable Development of Marine Fisheries, Ministry of Agriculture, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266071, PR China.
authors.forename: Meng
authors.initials: M
authors.lastname: Li
authors.forename: Ling
authors.initials: L
authors.lastname: Zhu
authors.forename: Chun-ya
authors.initials: CY
authors.lastname: Zhou
authors.forename: Shan
authors.initials: S
authors.lastname: Sun
authors.forename: Yan-jun
authors.initials: YJ
authors.lastname: Fan
authors.forename: Zhi-meng
authors.initials: ZM
authors.lastname: Zhuang
mesh_terms: D000595:Amino Acid Sequence; D000704:Analysis of Variance; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D023082:Defensins / Q000235:genetics* / Q000378:metabolism*; D020224:Expressed Sequence Tags; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000502:physiology*; D043143:Hepatopancreas / Q000378:metabolism; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D049894:Scapharca / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D017422:Sequence Analysis, DNA; D013997:Time Factors; D014733:Vibrio / Q000276:immunology*
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D023082:Defensins