Isolation, purification, characterization and glycan-binding profile of a d-galactoside specific lectin from the marine sponge, Halichondria okadai

Abstract A lectin recognizing both Galβ1-3GlcNAc and Galβ1-4GlcNAc was purified from the demosponge Halichondria okadai by lactosyl-agarose affinity chromatography. The molecular mass of the lectin was determined to be 30 kDa by SDS-PAGE under reducing and non-reducing conditions and 60 kDa by gel permeation chromatography. The p I value of the lectin was 6.7. It was found to agglutinate trypsinized and glutaraldehyde-fixed rabbit and human erythrocytes in the presence and absence of divalent cations. The hemagglutinating activity by the lectin was inhibited by d -galactose, methyl- d -galactopyranoside, N -acetyl- d -galactosamine, methyl- N -acetyl- d -galactosaminide, lactose, melibiose, and asialofetuin. The K d of the lectin against p -nitrophenyl-β-lactoside was determined to be 2.76 × 10 − 5  M and its glycan-binding profile given by frontal affinity chromatography was shown to be similar to many other known galectins. Partial primary structure analysis of 7 peptides by cleavage with lysyl endopeptidase indicated that one of the peptides showed significant similarity with galectin purified from the sponge Geodia cydonium .