Characterization and bioactivity analysis of a novel c-type lectin (LvLc1) from Pacific white shrimp (Litopenaeus vannamei)

As a family of carbohydrate binding proteins with Ca²⁺, C-type lectins play important roles in the first line of innate immune defense. In this research, a novel C-type lectin gene (LvLc1, GenBank Accession Number: KY937940) was cloned from Litopenaeus vannamei according to the data of shrimp transcriptome in our lab. The full-length cDNA consists of 1251 bp with an 891 bp open reading frame, encoding 296 amino acids. The deduced amino acid sequence contains a putative signal peptide of 19 amino acids. It also contains one carbohydrate recognition domains/C-type lectin-like domains (CRD). The potential carbohydrate-binding motif (QPD) presented in the CRD of LvLc1 may support its ability to bind galactose-type sugars. The deduced amino acid sequence of LvLc1 showed high identity with mannose-binding lectins of arthropod Procambarus clarkii and Pacifastacus leniusculus. It could be deduced that LvLc1 is a novel member of C-type lectin superfamily. The recombinant target protein (rLvLc1) was expressed by prokaryotic expression system. The LC-ESI-MS analysis showed that the peptide fragments of rLvLc1 were identical with the corresponding sequence of L. vannamei C-type lectin. rLvLc1 had agglutinating activity against main pathogens (G⁺, G^– and fungi) in aquaculture in a calcium-dependent manner. The agglutinating activity can be inhibited by multiple carbohydrates, such as galactose, mannose and lipopolysaccharide. These results suggest that LvLc1, as a Ca²⁺ dependent carbohydrate-recognition protein, is one of the important PRRs. It might play a crucial role in the innate immunity of the shrimp and it is expected to be applied to disease control.