Purification and Characterization of a D-Galactoside-Binding Lectin Purified from Bladder Moon Shell (Glossaulax didyma Roding)

To find novel carbohydrate-binding proteins (lectins) from marine invertebrates to understand the binding mechanism of the protein and to apply it for glycan-dependent diagnostics and/or glycoconjugates capture technology. A D-galactoside-binding lectin was purified from foot of bladder moon shell, Glossaulax didyma by lactosyl-agarose affinity chromatography. The crude supernatant by Tris-buffered saline had strong hemagglutination activity against trypsinized and glutaraldehyde-fixed human erythrocyte. However, the activity was not inhibited by any tested saccharides and chilete reagents. On the other hand, the dialyzed crude supernatant obtained from the precipitates with 100 mM lactose in Tris-buffered saline had also hemagglutination activity inhibited by b-galactoside and D-galactose. The lectin was purified with lactosyl-agarose affinity chromatography. The molecular mass of the lectin was determined to be 60 kDa by SDS-PAGE under reducing and non-reducing conditions and being a 60 kDa polypeptide monomer by gel permeation chromatography. The association-rate constant (k sub(ass)) and dissociation-rate constant (k sub(diss)) determined for the lectin against asialofetuin was determined as 5.4x10 super(4) M super(-1)sec super(-1) and 7.2x10 super(-3)sec super(-1), respectively. Lectin-conjugated Sepharose gel captured asialofetuin and eluted it by lactose-containing buffer from the gel, indicating that the lectin could catch the asialoglycoprotein. It was concluded that a many amount of a D-galactoside-binding lectin which can catch asialoglycoprotein presents in foot of the bladder moon shell.