Wheat germ agglutinin

A plant lectin found in wheat germ

Wheat germ agglutinin (WGA) is a lectin found in the germ of wheat (Triticum aestivum). It is a well-studied protein that binds specifically to N-acetylglucosamine and sialic acid residues, which are common components of the glycoproteins and glycolipids on the surface of eukaryotic cells.

Structure

Molecular structure of wheat germ agglutinin as visualized in Chimera.

Wheat germ agglutinin is a homodimeric protein, meaning it consists of two identical subunits. Each subunit contains a binding site for N-acetylglucosamine, allowing the protein to cross-link glycoproteins on cell surfaces. The structure of WGA has been elucidated through X-ray crystallography, revealing a compact, globular shape that facilitates its binding interactions.

Function

WGA is primarily known for its ability to bind to N-acetylglucosamine and sialic acid residues. This binding property makes it a useful tool in biochemistry and cell biology for labeling and isolating glycoproteins. WGA is often used in fluorescence microscopy to stain cell membranes, as it can bind to the glycoproteins present on the cell surface.

Applications

Wheat germ agglutinin has several applications in scientific research and biotechnology:

• Cell Labeling: WGA is used to label cell membranes in fluorescence microscopy due to its specific binding to glycoproteins.
• Glycoprotein Isolation: It is employed in the isolation and purification of glycoproteins from complex mixtures.
• Drug Delivery: WGA has been explored as a targeting agent in drug delivery systems, particularly for targeting drugs to specific cell types.

Role in Plant Biology

Arbuscule formation in plant roots, where WGA can play a role in plant-microbe interactions.

In plants, WGA is involved in defense mechanisms against pathogens. It can bind to the cell walls of invading organisms, inhibiting their growth and protecting the plant. Additionally, WGA is implicated in the formation of arbuscules, which are structures formed during mycorrhizal associations between plant roots and fungi. These associations are crucial for nutrient exchange and plant health.

Safety and Dietary Considerations

While WGA is a natural component of wheat, its presence in food has raised some concerns. Ingestion of large amounts of WGA can interfere with nutrient absorption and may cause gastrointestinal discomfort in sensitive individuals. However, typical dietary exposure through wheat products is generally considered safe for most people.

Related pages

• Lectin
• Glycoprotein
• Fluorescence microscopy
• Mycorrhiza