A T-antigen-binding lectin from Channa leucopunctatus (Murrel) plasma.

The plasma of Channa leucopunctatus, which agglutinates human A,B,O blood-group erythrocytes nonspecifically, contains three separate agglutinating activities that are distinguishable by hemagglutination with specific blood-group erythrocytes. Blood group A agglutinating activity of the plasma was separated from the other two hemagglutinating activities by DEAE-cellulose column chromatography and further purified to homogeneity by affinity chromatography on 2-acetamido-2-deoxy-D-galactose coupled to epoxy-activated Sepharose 6B. The apparent homogeneity of the lectin was established by poly(acrylamide) gel electrophoresis, isoelectric focusing, immunodiffusion, and cross-immunoelectrophoresis. The native protein has a mol. wt. of 140,000 and two identical subunits. The isoelectric point of the affinity-purified lectin is 4.6. Amino acid analysis indicated high proportions of glycine, alanine, and aspartic acid. The lectin is a glycoprotein and it has a requirement for divalent cations, Ca2+ and Mg2+ or Mn2+, for hemagglutinating activity. 2-Acetamido-2-deoxy-D-galactose, 4-nitrophenyl 2-acetamido-2-deoxy-alpha-D-galactopyranoside, T-antigenic disaccharide, and Forssman glycolipid are potent inhibitors.