CARBOHYDRATE AND GLYCOPROTEIN INTERACTIONS WITH LECTINS

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DESCRIPTION: The oligosaccharide chains of glycoproteins and glycolipids of normal and transformed cells have been implicated as receptors in a variety of biological processes, including cellular recognition, adhesion, differentiation and oncogenic transformation. The composition and structures of the oligosaccharides correlate with cell differentiation and transformation. Lectins are carbohydrate binding proteins which are found in a wide variety of organisms, including plants and animal cells. Lectins have been implicated in cellular recognition processes including apoptosis and metastasis. The long term objective is to gain insight into the structure-function roles of carbohydrate-lectin recognition interactions in normal and transformed cells. Binding of lectins to cell surfaces often leads to cross-linking of glycoconjugate receptors, including glycoproteins and glycolipids, which in many cases is related to the biological responses of cells. Certain oligosaccharides isolated from the glycoproteins and glycolipids are multivalent and form cross-linked complexes with lectins. This leads to an important new dimension of specificity in carbohydrate-protein interactions: namely, the formation of unique, homogeneous cross-linked complexes between carbohydrates and lectins, even in the presence of mixtures of the molecules. The cross-linked complexes are often crystalline and amenable to high resolution x-ray and neutron diffraction studies. The specific aims are to 1) determine the atomic structures of a single lectin cross-linked with a series of multivalent carbohydrates, 2) investigate the cross-linking activities of animal lectins, 3) explore the cross-linking activities of lectins on the surface of transformed cells, and 4) probe the solution binding specificities of lectins. The results, in turn, will provide insight into structure-function relationships of lectin-carbohydrate interactions in normal and transformed cells.