The thrust of this proposal is directed at establishing the molecular basis of protein-carbohydrate interactions using the paradigm of the carbohydrate-binding proteins of plant and animal origin (lectins). The underlying hypothesis is that such binding involves specific, well-defined interactions between functional groups of the carbohydrate ligand in its ground-state structure and matching groups in the protein forming a specific binding site, which provides for any degree of specificity of a lectin for a specific carbohydrate ligand. The application of lectin- carbohydrate binding to biomedical problems is a significant consideration of our studies. Several new techniques that provide unique new approaches for studying protein-carbohydrate interaction include submicro frontal chromatography analysis, surface plasmon resonance, and mathematical modeling of the combining sites of lectins. Another innovation is an extension of our successful study of DNA-carbohydrate interaction in which we will attempt to obtain nucleic acid aptamers to human blood group substances and the bacterial polysaccharide from E.coli 0139 which causes """"""""traveler's disease."""""""" Among the objectives we plan to pursue are a search for (and isolation and characterization) of new lectins, with unique and useful properties; a physical-chemical characterization of the sialic acid binding slug lectin, including expression of the recombinant proteins in a eukaryotic expression system, NMR measurements of the binding of methyl N-acetylneuraminic acid alpha-ketoside and a solution of its X-ray crystal structure complexed with neuraminic acid; the X-ray crystal structure of the Man alpha1-3 Man-specific crocus lectin complexed with its disaccharide, and its use as a histochemical stain for animal cells and tissues; and attempts to label the carbohydrate binding sites of several lectins using photoaffinity labels.
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