About the Lectin

A crude extract of a specific hybrid (Apeldoorn) of tulip bulbs is able to agglutinate human and rabbit erythrocytes. Although the extract activity is not blood group specific, type O erythrocytes are agglutinated more readily than either A or B cells. Simple sugars do not inhibit the activity of the crude extract 1 . Fetuin, asialofetuin, and thyroglobulin are all inhibitors of agglutination. Because of this finding, the lectin has been purified to homogeneity on immobilized fetuin, rather than on an immobilized carbohydrate. The purified lectin exhibits the same basic agglutination properties as the crude extract. Rabbit erythrocytes are agglutinated more readily than human erythrocytes. As with the lectin from Colchicum autumnale (CA), simple sugars such GalNAc, lactose, and galactose are potent inhibitors of the purified tulip lectin for human erythrocytes. These same sugars do not inhibit the agglutination of rabbit cells by the pure lectin, although thyroglobulin, fetuin, and asialofetuin are inhibitory. Ovomucoid will also inhibit rabbit erythrocyte agglutination by the pure lectin, but only weakly. It has been suggested that components of the crude extract prevent inhibition of the lectin by simple carbohydrates. When these components are removed by purification of the lectin, the purified TL reaction with human erythrocytes can be inhibited by simple sugars. Like CA, the tulip lectin is also a strong mitogen for human lymphocytes 2 .

Bulbs of a species of tulip, T. gesneriana (which is a parent of the Apeldoorn hybrid) contains a lectin specific for mannose oligosaccharides containing an α(1,6)-linkage, and which agglutinates yeast cells, but not animal or human erythrocytes 3 . It has now been shown that this mannose binding lectin is also present in the Apeldoorn hybrid(TxLMII) 4 . It is a tetramer of identical subunits (17kDa) which recognize mannose, mannose-6-phosphate, fucose, and fucosamine 3,4 . Genes for both TxMII and the original lectin of the complex specificity (TxLCI) have been cloned and found to have highly homologous amino acid sequences. Futhermore, the subunit of TxLCI (28kDa) possesses both a mannose-binding site and an N-acetylgalactosamine binding site 4 . T. gesneriana, on the other hand, also contains a lectin of complex specificity, but it agglutinates only mouse and rat erythrocytes, and is apparently a heterodimer with subunits of 26kDa and 14 kDa 5 . This lectin also is a potent mitogen, which activity resides in the 26kDa subunit 6 .

REFERENCES

  1. Cammue, B. P. A., et al. (1986) Planta. 169 : 583-588.
  2. Kilpatrick, D. C., et al. (1988). Poster Abstract, Interlec X, Prague, Czechoslovakia.
  3. Oda, Y. and Minami, K. (1986) Eur. J. Biochem. 159 : 239-245.
  4. Van Damme, E.J., et al. (1996) Eur. J. Biochem. 236 : 419-427.
  5. Oda, Y., et al. (1987) Eur. J. Biochem. 165 : 297-302.
  6. Oda, Y., et al. (1991) Chem. Pharm. Bull. 39 : 3350- 3352.

Product Characteristics
Buffer 0.05M Tris – 0.1M NaCl, pH 8.7.
Blood Group Non-specific. O > A > B.
Activity At a concentration of 1 mg ml pure TL does not visibly agglutinate human type A, B, or O blood cells. Less than 250 μg/ml will agglutinate neuraminidase treated type O cells.
Inhibitory Carbohydrate N-acetyl‑D‑galactosamine > Lactose > Galactose.
Molecular Weight Two lectin forms with aggregate molecular weights of 120,000 and 60,000 Da are apparent when the lectin is analyzed by gel filtration. Both of these forms give a single band of MW=28,000 by SDS-PAGE.
Caution The purified, lyophiized lectin is only slightly soluble in water.