A serum fucolectin isolated and characterized from sea bass Dicentrarchus labrax

A lectin specific for fucose and galactose was isolated by affinity chromatography on Sepharose CL-6B from the serum of Dicentrarchus labrax. The hemagglutinating activity against rabbit erythrocytes was calcium-independent, and reached its maximum at 37°C. Two protein components were found in the hemagglutinating fractions eluted from the Sepharose column. Only the 34 kDa component (DLL2) eluted from the polyacrylamide gels (SDS-PAGE) showed agglutinating activity against rabbit erythrocytes. SDS-PAGE, in non-reducing conditions, revealed a single 66 kDa protein that reacted with antibodies to the 34 kDa component. Therefore, a dimeric structure stabilized by disulfide bonds can be proposed. The Ca 2+-independent fucose-binding specificity, a significant amino acid sequence homology of the N-terminal trait, and cross-reaction of eel fucolectin with antibodies to DLL2 suggest that this lectin may be included in the recently identified fucolectin family.