A novel C-type lectin from crab Eriocheir sinensis functions as pattern recognition receptor enhancing cellular encapsulation

C-type lectins are a large family of Ca2+-dependent carbohydrate binding proteins which play crucial roles to recognize and eliminate pathogens in innate immunity. In the present study, a novel C-type lectin was identified from Eriocheir sinensis (designated as EsCTL). The full-length cDNA of EsCTL was of 789 bp with an open reading frame of 468 bp encoding a polypeptide of 156 amino acids with a signal sequence and single carbohydrate-recognition domain (CRD). The potential tertiary structure of the CRD adopted a typical double-loop structure with Ca2+-binding site 2 in the long loop region and two conserved disulfide bridges at the bases of the loops. An EPQ motif to determine carbohydrate binding specificity was identified in the CRD of EsCTL. The mRNA transcripts of EsCTL were mainly detected in hepatopancreas and its relative expression level in hemocytes was significantly up-regulated after the challenges of Vibrio anguillarum (P