Wheat germ agglutinin (WGA) is a

lectin Lectins are carbohydrate-binding proteins that are highly specific for sugar Moiety (chemistry), groups that are part of other molecules, so cause agglutination (biology), agglutination of particular cells or precipitation of glycoconjugates an ...

that protects wheat (''

Triticum Wheat is a group of wild and domesticated grasses of the genus ''Triticum'' (). They are cultivated for their cereal grains, which are staple foods around the world. Well-known wheat species and hybrids include the most widely grown comm ...

'') from insects, yeast and bacteria. An

agglutinin An agglutinin is a substance in the blood that causes particles to coagulate and aggregate; that is, to change from fluid-like state to a thickened-mass (solid) state. Agglutinins can be antibodies that cause antigens to aggregate by binding t ...

protein, it binds to N-acetyl-D-glucosamine and

sialic acid Sialic acids are a class of alpha-keto acid sugars with a nine-carbon backbone. The term "sialic acid" () was first introduced by Swedish biochemist Gunnar Blix in 1952. The most common member of this group is ''N''-acetylneuraminic acid ...

. WGA has also been shown to interact with sialic acid residues on oligosaccharides. Succinylated WGA is selective for β-N-acetylglucosamine (β-GlcNAc), making it a useful tool for detecting ''O''-GlcNAc. WGA is composed of a mixture of three isoforms (WGA1, WGA2, WGA3), which are quite similar to each other and each contain an unusually high amount of glycine. These three isoforms vary at a total of 10 amino acid positions and all have dimeric structures with four domains per monomer. Each domain (WGA.A, WGA.B, WGA.C, WGA.D) is hevein-like and is stabilized by a disulfide bond. N-acetyl-D-glucosamine in the natural environment of wheat is found in the

chitin Chitin (carbon, C8hydrogen, H13oxygen, O5nitrogen, N)n ( ) is a long-chain polymer of N-Acetylglucosamine, ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is the second most abundant polysaccharide in nature (behind only cell ...

of insects, and the

cell membrane The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extr ...

of yeast & bacteria. WGA is found abundantly—but not exclusively—in the wheat kernel, where it got the 'germ' name from. In mammals the N-acetyl-D-glucosamine that WGA binds to is found in

cartilage Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

and

cornea The cornea is the transparency (optics), transparent front part of the eyeball which covers the Iris (anatomy), iris, pupil, and Anterior chamber of eyeball, anterior chamber. Along with the anterior chamber and Lens (anatomy), lens, the cornea ...

among other places. In those animals

is found in mucous membranes, e.g. the lining of the inner nose, and digestive tract. In solution, WGA exists mostly as a heterodimer of 38,000 daltons. It is cationic at physiological pH. It contains a

Carbohydrate-binding module In molecular biology, a carbohydrate-binding module (CBM) is a protein domain found in carbohydrate-active enzymes (for example glycoside hydrolases). The majority of these domains have carbohydrate-binding activity. Some of th ...

called CBM18.

Use in molecular biology

WGA is also widely used in biological research, particularly in the field of

glycobiology Defined in the narrowest sense, glycobiology is the study of the structure, biosynthesis, and biology of saccharides (sugar chains or glycans) that are widely distributed in nature. Sugars or saccharides are essential components of all living thin ...

. Since WGA binds to glycoconjugates, it can be used to label cell membranes, fibrotic scar tissue and

arbuscular mycorrhizae An arbuscular mycorrhiza (AM) (plural ''mycorrhizae'') is a type of mycorrhiza in which the symbiont fungus (''Arbuscular mycorrhizal fungi'', or AMF) penetrates the cortical cells of the roots of a vascular plant forming arbuscules. Arbuscul ...

for imaging and analysis. WGA is fairly stable in acidic solutions, and can be resistant to proteolysis. WGA has also demonstrated some cytotoxicity and has thus been used in recent research involving hematological cancers, particularly acute myeloid leukemia. In addition, WGA has been thought to improve drug delivery due to its ability to cross the blood-brain barrier, but research has yet to be performed on this hypothesis.

References

Lectins {{protein-stub

Use in molecular biology

See also

References