Wheat germ agglutinin (WGA) contains a group of closely related isolectins, with an isoelectric point about pH 9. The receptor sugar for WGA is N-acetylglucosamine, with preferential binding to dimers and trimers of this sugar. WGA can bind oligosaccharides containing terminal N-acetylglucosamine or chitobiose, structures which are common to many serum and membrane glycoproteins. Bacterial cell wall peptidoglycans, chitin, cartilage glycosaminoglycans, and glycolipids can also bind WGA. Native WGA has also been reported to interact with some glycoproteins via sialic acid residues (see succinylated WGA). This lectin is used for the purification of insulin receptors and for neuronal tracing.
Agarose bound* WGA is prepared using our affinity-purified lectins. Heat stable, cross-linked 4% agarose beads with a molecular weight exclusion limit of about 2x107 daltons are used as the solid-phase matrix to which the lectins are covalently coupled. The attachment of the lectins to the beads is carefully controlled to preserve lectin activity and minimize conformational changes of the bound lectins that might result in nonspecific ionic or hydrophobic interactions. The technique we have developed to couple lectins to agarose beads inserts a hydrophilic spacer arm between the lectin and the matrix.
This coupling method provides several advantages over the traditional cyanogen bromide procedure:
Maximum carbohydrate binding activity of the coupled lectins is retained
Linkage is stable over a range of pH values
Conjugated proteins are not leached off the beads by Tris or other routinely used buffers
No residual charges are present after conjugation. This minimizes non-specific binding to the matrix.
Our agarose bound lectins are supplied at a constant concentration of lectin per ml of settled beads. The concentration for each lectin is selected to achieve the highest glycoconjugate binding capacity per mg of lectin present in the beads. Each lot is tested for its binding capacity using glycoproteins known to bind the lectin. This provides a guideline for the user and assures the quality of our agarose bound lectins.
Inhibiting/Eluting Sugar: Chitin Hydrolysate or 500 mM N-acetylglucosamine with salt and/or acid elution generally required