Molecular cloning and immune responsive expression of a novel C-type lectin gene from bay scallop Argopecten irradians

C-type lectins are Ca2+-dependent carbohydrate-recognition proteins that play crucial roles in innate immunity. The cDNA of C-type lectin (AiCTL1) in the bay scallop Argopecten irradians was cloned by expressed sequence tag (EST) and RACE techniques. The full-length cDNA of AiCTL1 was 660 bp, consisting of a 5′-terminal untranslated region (UTR) of 30 bp and a 3′ UTR of 132 bp with a polyadenylation signal sequence AATAAA and a poly(A) tail. The AiCTL1 cDNA encoded a polypeptide of 166 amino acids with a putative signal peptide of 20 amino acid residues and a mature protein of 146 amino acids. The deduced amino acid sequence of AiCTL1 was highly similar to those of the C-type lectins from other animals and contained a typical carbohydrate-recognition domain (CRD) of 121 residues, which has four conserved disulfide-bonded cysteine residues that define the CRD and two additional cysteine residues at the amino terminus. AiCTL1 mRNA was dominantly expressed in the hemocytes of the bay scallop. The temporal expression of AiCTL1 mRNA in hemocytes was increased by 5.7- and 4.9-fold at 6 h after injury and 8 h after injection of bacteria, respectively. The structural features, high similarity and expression pattern of AiCTL1 indicate that the gene may be involved in injury healing and the immune response in A. irradians.