About the Lectin

A lectin present in the seeds of the osage orange has been purified and has a specificity for galactose and N-acetyl-D-galactosamine. The lectin can be resolved into five different isolectins 1 . Like Jacalin, the lectin has an α 4 β 4 structure that shows far greater micro-heterogeniety than plant lectin from other families, due to multiple genetic isoforms and posttranslational processing 2 . The subunits have been sequenced 2,3 and are highly homologous to Jacalin. In the presence of a ligand, Galβ1,3GalNAc (T-antigen disaccharide), an isoform of the lectin appears to crystallize as a dimer 4 . The nominal carbohydrate specificity of MPA is similar to that of GS-I. However, while GS-I is a blood group B specific lectin, MPA reacts most strongly with type O and A cells. Also, while neuraminidase treatment of the erythrocytes increases their reactivity with MPA, GS-I is only slightly more reactive with treated cells. Purified MPA is a very stable lectin, maintaining activity when heated to 75°C. MPA is also resistant to detergent and alkali denaturation 5 . The lectin reacts well with terminal, non-reducing carbohydrates. MPA has been shown to react with certain bacterial polysaccharides 6 and the anti-freeze glycoprotein 7 . This indicates that MPA will also react with internal GalNAc residues. Pure MPA is cytotoxic for several cell types; it induces cytotoxic activity in female Lewis and Brown Norway rat spleen cells. When compared to either Con A or PHA-E, MPA promotes a greater cytotoxic effect toward red blood cells of guinea pigs, rabbits and humans 9 . The cytotoxic effect is apparently related to the carbohydrate specificity, since melibiose inhibits both agglutination and cytotoxicity. MPA has been used in mitogenic and binding studies of rat T cells 9 . MPA is a specific marker for a glycoprotein on type 2 aveolar epithelial cells 10 . It is known to have a high affinity for the primary intramembranous bone matrix 11 , and specifically labels membranocystic lesions in membranes lipodystrophy (Nasu-Hakola disease) 12 .

REFERENCES

  1. Bausch, J. N., et al. (1981) Biochemistry. 20 : 2618-2620.
  2. Young, N.M., et al. (1995) Glycoconj J. 12 : 135-141.
  3. Young. N.M., et al. (1991) FEBS Lett. 282 : 382-384.
  4. Lee, X., et al. (1989) J. Mol. Biol. 210 : 685-686.
  5. Jirgensons, B. (1980) Biochim. Biophys. Acta. 625 : 193.
  6. Allen, P. Z. (1985) Infect. Immunol. 47 : 90-93.
  7. Chuba, J. V. and Kuhns, W. (1973) Nature (London).242 : 342.
  8. Jones, J. M. and Soderberg, F. (1979) Cell. Immunol.42 : 319-326.
  9. Jones, J. M. and Feldman, J. D. (1973) J. Immunol.111 : 1765.
  10. Marshall, B. C., et al. (1988) Biochem. Biophys. Acta 966 : 403-413.
  11. Suzuki, O., et al. (1993) Bone and Mineral 20 : 151-166.
  12. Katajima, I., et al. (1988) Virchows Archiv A. 413 : 475-483.

Product Characteristics
Buffer 0.01M Phosphate – 0.15M NaCl, pH 7.2-7.4.
Blood Group Nonspecific. O > A > B.
Activity Less than 5 μg/ml will agglutinate type O human erythrocytes. Less than 0.1 μg/ml will agglutinate neuraminidase treated cells.
Inhibitory Carbohydrate α-D-galactose. Melibiose [Galα (1,6)Glc] is a more potent inhibitor, as is T.disaccharide [Galβ1,3GalNAc]
Molecular Weight 40-46,000 Da as determined by gel filtration. Subunit MW=14,700 and 2,200. When analyzed by SDS-PAGE at pH 8.6 a single band of MW=54-60,000 is usually stained.