Isolation and characterization of a novel fucose-binding lectin from the gill of bighead carp (Aristichthys nobilis)

Lectins play an important role in many biological systems and are used increasingly in human disease therapy. To improve our understanding of fish lectins we purified and characterized a fucose-binding lectin from the gill of bighead carp (Aristichthys nobilis). The purification procedure consisted of extracting soluble proteins in 25 mM Tris–HCl buffer (pH 8.5), separation on a DEAE-Sepharose FF ion exchange column, followed by gel filtration chromatography on Sephacryl S-200 HR and Superdex 200 10/300 GL columns. The purified lectin, designated GANL, had a single protein band with an apparent molecular mass of 37 kDa when subject to SDS-PAGE under reducing conditions. GANL is a homomultimeric glycoprotein with a native molecular mass of 220 kDa and a carbohydrate content of ∼13.4%. The purified lectin only agglutinated rabbit native erythrocytes, and did not require Ca2+. Its activity was not inhibited by any of the mono- or disaccharides or glycoproteins tested, except for fucose. GANL contains a high proportion of Asp, Glu, Leu, Val, and Lys. The first 10 residues of the N-terminal region were determined as AGEQGGQCSA. The anti-microbial activity was assessed by measuring agglutination and inhibition of pathogen growth. Our results suggest that GANL agglutinates and inhibits the growth of Vibrio harveyi but has no antifungal activity.