About the Lectin
The ground elder lectin has been purified by a combination of affinity and ion-exchange chromatography. This lectin has been partially characterized with regard to its carbohydrate specificity and molecular composition 1 . The lectin is a major constituent of ground elder rhizomes, accounting for as much as 5% of the total protein weight. Crude rhizome extracts agglutinate human erythrocytes regardless of blood type. The agglutination reaction is inhibited by GalNAc and lactose, but APP does not bind to either of these carbohydrates when they are immobilized on a support matrix. Affinity matrices such as fetuin and cross-linked arabinogalactan, which have been used to isolate other GalNAc specific lectins, have not proved effective for the isolation of APP. The lectin can be readily purified on immobilized blood group A membrane glycoproteins. Although APP is readily inhibited by simple sugars in solution, it actually has a poorly understood specificity for complex glycoconjugates. Analysis of the molecular composition of APP indicates that it is perhaps the largest lectin yet discovered. It is an octamer composed of a single subunit, with an apparent molecular weight of 60,000 Da. The aggregate molecular weight of 480,000 Da exceeds that of LPA by 30%, and APP is perhaps three times larger than any other plant lectin. Electron microscopic analysis of purified APP has been performed, indicating that large protein particles greater than 5 million Da exist in the preparation. These are possibly polymeric forms of the lectin 2 . Gel filtration to separate the higher and lower molecular weight components of APP, followed by SDS-PAGE analysis, has shown that the 5 million Da particle is composed of the same subunit as the lower molecular weight protein. Gel filtration and sucrose density gradient centrifugation have been combined to show that the large protein particles are in fact components of the purified lectin and not artifacts from processing the lectin for electron microscopy. APP has been used in typing β-hemolytic streptococci 3 .
- Peumans, W. J., et al. (1985) Planta. 164 : 75-82.
- Leurentop, L., et al. (1987) Planta. 172 : 14-19.
- Kellens, J.T.C., et al. (1993) J. Med. Microb. 39 : 440-445
|Buffer||0.01M Phosphate – 0.15M NaCl, pH 7.2-7.4.|
|Inhibitory Carbohydrate||N-acetyl‑D‑galactosamine > Lactose >> Galactose.|
|Molecular Weight||Aggregate MW=480,000 (approximate). Two bands of MW=55,000 and 60,000 when analyzed by SDS-PAGE. Higher molecular weight species (>5 million Da) are present in samples analyzed by gel filtration.|