Identification and characterisation of a novel small galectin in razor clam (Sinonovacula constricta) with multiple innate immune functions

Abstract Galectins are lectins possessing an evolutionarily conserved carbohydrate recognition domain (CRD) with affinity for β-galactoside. The key role played by innate immunity in invertebrates has recently become apparent. Herein, a full-length galectin (ScGal) was identified in razor clam ( Sinonovacula constricta ). The 528 bp open reading frame encodes a polypeptide of 176 amino acids with a single CRD and no signal peptide. ScGal mRNA transcripts were mainly expressed in hemolymph and gill, and were significantly up-regulated following bacterial challenge. Recombinant rScGal protein binds to and aggregates various bacteria, and has affinity for peptidoglycan, lipoteichoic acid and d -galactose. The protein also stimulates hemocytes to phagocytose invading bacterial pathogens. ScGal is an important immune factor in innate immunity, and a small protein with multiple important functions.