title: AiCTL-6, a novel C-type lectin from bay scallop Argopecten irradians with a long C-type lectin-like domain.
abstract: C-type lectins are a superfamily of carbohydrate-recognition proteins which play crucial roles in the innate immunity. In this study, a novel C-type lectin gene from scallop Argopecten irradians (designated as AiCTL-6) was cloned by rapid amplification of cDNA ends (RACE) approach based on expression sequence tag (EST) analysis. The full-length cDNA of AiCTL-6 was 1080 bp. The open reading frame encoded a polypeptide of 307 amino acids, including a signal sequence and a C-type lectin-like domain (CTLD) of 150 amino acid residues longer than any usual CTLD. It contained six conserved cysteine residues involved in the formation of three internal disulfide bridges and an EPD (Glu(269)-Pro(270)-Asp(271)) motif at the Ca(2+)-binding site 2. The deduced amino acid sequence of AiCTL-6 showed high similarity to members of C-type lectin superfamily. By fluorescent quantitative real-time PCR, AiCTL-6 mRNA was found mainly in hepatopancreas and gill, and marginally expressed in other tissues. After the scallops were challenged by Listonella anguillarum for 6 h, the mRNA expression of AiCTL-6 was up-regulated significantly to 7.2-fold compared to the blank group. While at 9 h post Micrococcus luteus challenge, its expression level was 60.1 times higher than that of the blank group. The functional activity of AiCTL-6 was investigated by recombination and expression of the cDNA fragment encoding its mature peptide in Escherichia coli Rosetta gami (DE3). The recombinant AiCTL-6 could agglutinate Gram-negative bacteria E. coli TOP10F', Gram-positive bacteria M. luteus and Staphylococcus aureus. These results collectively suggested that AiCTL-6, as a novel member of C-type lectin family, contributed to the host defense mechanisms against invading microorganism in A. irradians.
authors.affiliation: The Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
authors.forename: Huan
authors.initials: H
authors.lastname: Zhang
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Song
authors.forename: Lingling
authors.initials: L
authors.lastname: Wang
authors.forename: Pengfei
authors.initials: P
authors.lastname: Kong
authors.forename: Jialong
authors.initials: J
authors.lastname: Yang
authors.forename: Lin
authors.initials: L
authors.lastname: Liu
authors.forename: Limei
authors.initials: L
authors.lastname: Qiu
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Lihua
authors.initials: L
authors.lastname: Qiu
authors.forename: Linsheng
authors.initials: L
authors.lastname: Song
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005786:Gene Expression Regulation / Q000502:physiology; D037102:Lectins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D049897:Pectinidae / Q000276:immunology / Q000378:metabolism*; D010802:Phylogeny; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
chemical_list: D018076:DNA, Complementary; D037102:Lectins