Immunological significance of metal induced conformational changes in the mitogenic AchatininH binding to carbohydrate ligands

9-O-Acetyl neuraminic acid specific lectin (Achatinin_H) was isolated from the hemolymph of the land snail Achatina fulica by affinity chromatography on sheep submaxillary mucin (SSM) coupled cyanogen bromide activated Sepharose 4B. The molecular weight of the native protein was 2.42 kDa. UV-Vis absorption, fluorescence and circular dichroism spectroscopic studies on Achatinin_H revealed the importance of divalent metal ions (Ca²⁺, Mg²⁺ and Mn²⁺) on lectin conformational change associated with activity of lectins. The binding of these cations changes λ_max to shorter wavelength in the far UV region (blue shift) and longer wavelength in UV region (red shift), indicating substantial contribution of aromatic side chain in the far UV region on binding with metal ions. The results infer that divalent cations cause conformational changes in lectin which may be responsible for affinity with their carbohydrate moiety.