About the Lectin
Seeds of the Japanese pagoda tree have been shown to contain a blood group specific lectin with some interesting requirements for binding. Hemagglutination takes place only above pH 8.3 with a pH optimum of 8.3-9.0 1 . In contrast to this finding, the lectin is precipitated by blood group substances between pH 6.7-9.5. EDTA reversibly inactivates the lectin, which reportedly requires Ca ++ , Mg ++ , or Mn ++ for binding 2 . This finding contrasts with hemagglutination studies performed at EY Laboratories. A buffer devoid of these ions, but at the proper pH, is sufficient to permit agglutination by the lectin. Additional ions may enhance the reaction, however, their absence is not sufficient to prevent lectin binding. Purified SJA will agglutinate both human type A and B erythrocytes. Since the reaction is much stronger with type B erythrocytes a specific anti-B lectin can be prepared by appropriate dilution of SJA. The lectin does not react with normal type O red blood cells. After neuraminidase treatment of the O cells, lectin induced agglutination is comparable to that seen with B erythrocytes. A lectin subunit of MW=33,000 is found when the lectin is analyzed by SDS-PAGE at pH 4.4. However, when run under the same conditions at pH 8.4, multiple forms in equilibrium may appear 3 . This is in agreement with results obtained by EY Laboratories. Although single band purity is obtained, the molecular weight can vary between 40-60,000 Da. Generally, SJA reacts stronger with GalNAc than other mono-saccharides tested. Galactose linked either β(1,3) or β(1,4) to a subterminal sugar is a more potent inhibitor than GalNAc alone 2 . GalNAc β(1,6) galactose is 15 times more inhibitory than GalNAc alone 4 . The seed lectin gene has been cloned and sequenced. It is the product of a single gene, which is highly homologous, but not identical to a similar lectin found in the bark 5 . The bark also contains one or more mannose-specific lectins 6 .
- Poretz, R. D., et al. (1974) Biochemistry. 13 : 250-256.
- Wu, A. M., et al. (1981) Arch. Biochem. Biophys.209 : 191-203.
- Poretz, R. D. (1973) Meth. Enzymol. 28 : 349-354.
- Allen, H. J., et al. (1980) Carbohydrate Res. 86 : 123-131.
- Van Damme, E.J.M., et al. (1997) Plant Mol. Biol. 33 : 523-536.
- Ueno, M., et al. (1991) J. Biol. Chem. 266 : 3146-3153.
|Buffer||0.05M Tris – 0.15M NaCl, pH 8.7|
|Blood Group||B >> A.|
|Activity||Less than 30 μg/ml will agglutinate human type B erythrocytes.|
|Inhibitory Carbohydrate||N-acetyl‑D‑galactosamine > galactose.|
|Molecular Weight||Dimer of aggregate MW=65,000. A single band between 40-60,000 Da appears on SDS‑PAGE.|