Purification and characterization of a T-antigen specific lectin from the coelomic fluid of a marine invertebrate, sea cucumber (Holothuria scabra)

A novel lectin was purified from the coelomic fluid of the sea cucumber Holothuria scabra (HSL), subjected to bacterial challenge. HSL is a monomeric glycoprotein of molecular mass 182 kDa. The lectin is highly thermostable as it retains full activity for 1 h at 80 °C. Further, the hemagglutination activity of HSL is unaffected by pH in the range 2–11. Unlike other lectins purified from marine invertebrates, the hemagglutination activity of HSL does not require any divalent metal ions. The affinity profile of HSL was studied by a combination of hemagglutination inhibition and fluorescence spectroscopy. HSL binds to desialylated glycoproteins, MeαGal, T-antigen and T (α-ser)-antigen with a distinction between β1–4 and β1–3 linkages. Meα-T-antigen was a potent ligand having highest affinity (Ka 8.32 × 107 M−1). Monosaccharide binding is enthalphically driven while disaccharide binding involves both entropic and enthalpic contributions.