Identification and molecular characterization of a mucosal lectin (MeML) from the blue mussel Mytilus edulis and its potential role in particle capture.

Molecular recognition of food particles has been suspected to play an important role in particle selection in suspension feeding bivalves. Lectins are a group of sugar-binding proteins that are widely involved in biological recognition. They have been reported in mucus covering bivalves feeding organs and were recently shown to mediate particle sorting in these animals. In this study, we report a novel putative C-type lectin from the blue mussel Mytilus edulis. The cDNA of this lectin (hereby designated MeML for M. edulis mucocyte lectin) is 459bp long encoding a 152-residue protein. MeML presents a signal peptide and a single carbohydrate recognition domain (CRD) which contains a QPS (Gln, Pro, and Ser) motif and two putative conserved sites, WND and ENC, for calcium binding. MeML was expressed in mucocytes lining the epithelium of pallial organs (gills, labial palps and mantle) and intestine, and its expression was significantly up-regulated following starvation. MeML transcript was not detected in other tissues including hemocytes. MeML is suspected to play a role in the capture of food particle which further support the involvement of this lectin in particle selection mechanism.