InterPro domain: IPR036242

Agglutinins are sugar-specific lectins that can agglutinate erythrocytes and other cell types. Lectins occur widely in plants, as well as some microorganisms and animal [ 1 ]. Agglutinin from Amaranthus caudatus (amaranthin) is a lectin from the ancient South American crop, amaranth grain. Although its biological function is unknown, it can agglutinate A, B and O red blood cells, and has a carbohydrate-binding site that is specific for the methyl-glycoside of the T-antigen found linked to serine or threonine residues of cell surface glycoproteins [ 2 ]. The protein is comprised of a homodimer, with each homodimer consisting of two beta-trefoil domains [ 3 ]. Lectin B chains from ricin and related toxins also contain beta-trefoil domain, however they are not related to agglutinin, showing little sequence similarity [ 4 ].

1. History of lectins: from hemagglutinins to biological recognition molecules. Glycobiology 14, 53R-62R
2. Physicochemical properties of amaranthin, the lectin from Amaranthus caudatus seeds. Biochemistry 29, 10555-61
3. Isolation and characterization of amaranthin, a lectin present in the seeds of Amaranthus caudatus, that recognizes the T- (or cryptic T)-antigen. J. Biol. Chem. 264, 16123-31
4. Structure of benzyl T-antigen disaccharide bound to Amaranthus caudatus agglutinin. Nat. Struct. Biol. 4, 779-83