Purification and some characteristics of a β‐galactoside binding soluble lectin from amphibian ovary

Abstract
Soluble extracts of Bufo ovaries agglutinate sialidase‐treated rabbit erythrocytes. Unlike other amphibian lectins this agglutination activity does not require the presence of calcium ions. It is specifically inhibited by D‐galactose and its derivatives. Thiodi‐D‐galactoside is the most potent saccharide inhibitor followed by lactose and methyl‐β‐D‐galactoside, respectively. D‐Fucose, D‐glucose and D‐mannose do not inhibit the activity at concentrations at or above 100 mM. The lectin has been purified 500‐fold to apparent homogeneity from the ovaries by salt extraction and affinity chromatography on lactose‐aminophenyl‐agarose, with a yield of about 0.2%. The molecular mass determined by gel filtration under native conditions was 30 kDa; polyacrylamide gel electrophoresis in SDS gave a molecular mass of 15 kDa, suggesting that the lectin is a dimer. The lectin has an isoelectric point of 40 and contains a high proportion of acidic amino acids.