About the Lectin
Agglutinating activity in crude extracts of the pea tree, Caragana arborescens, were first described by Makela1. Two lectins with slightly different binding specificities and reactivities have been purified by affinity chromatography 2 . These lectins are referred to as CAA-I and CAA-II. The only apparent difference between the two lectins is the absence of fucose in CAA-I. The purified lectins are not blood group specific; however, reactivity is enhanced dramatically by treatment of the erythrocytes with neuraminidase. The lectins react weakly with type A and B human erythrocytes and about 4 times more strongly with type O cells. Apparently CAA-I is responsible for more than 99% of the hemagglutinating activity. CAA-II does not appear to exhibit much agglutinating activity itself. It does appear to be able to bind to cells since the addition of large excesses of this lectin can inhibit the agglutinating activity of CAA-I slightly. Since CAA-II is not a strong agglutinin, any agglutinating activity may actually be due to contamination with CAA-I. While most lectins react with complex saccharide structures better than with simple sugars, CAA-I is more strongly inhibited by monosaccharides. It is therefore assumed that the carbohydrate binding site is relatively small on this lectin. CAA-I has a high affinity for N-acetyl-D-galactosamine, although galactose at high concentrations may be as potent an inhibitor. CAA-II has been shown to bind agarose beads more readily than CAA-I, indicating that it has a greater affinity for galactose than CAA-I, but the carbohydrate specificity has not yet been detemined. Both lectins agglutinate normal and transformed mouse cells to the same extent. This may be useful in the study of cell growth and differentiation due to the lack of toxicity of either lectin toward mouse fibroblast cells 2 . The agglutinating property of these two lectins for mouse cells is in contrast to the properties of several other galactose and GalNAc specific lectins which agglutinate transformed cells preferentially 3,4 . CAA-I is reported to be a tetramer of MW=103,000 while CAA-II is a dimer of MW=64,000. The purified lectin preparation offered by EY Laboratories contains a mixture of the two lectins.
- Makela, O. (1957). Ann. Med. Exp. Biol. Fenn.35 (Suppl.11).
- Bloch, R., et al. (1976). J. Biol. Chem. 251 : 5929-5935.
- Nicolson, G. L., et al. (1974). Biochem. 9 : 196-204.
- Lis, H., et al. (1970). Biochem. Biophys. Acta. 211 : 582.
|Buffer||0.01M Phosphate – 0.15M NaCl, pH 7.2-7.4.|
|Activity||1-2 μg/ml will agglutinate human erythrocytes after neuraminidase treatment of the cells.|
|Inhibitory Carbohydrate||N-acetyl-D-galactosamine (CAA-I) Not determined (CAA-II)|
|Molecular Weight||CAA-I has a MW = 103,000. CAA-II has a MW = 64,000.|