In spite of the many dramatic advances being made in medical care, diseases related to the genus Mycobacteria continue to plague largeareas of the world. The long-range objective of this research program is to contribute to our understanding of the fundamental physiology of mycobacteria with the belief that this understanding can lead to improved procedures for treating and controlling tuberculosis and leprosy. The core of the program is centered on the fact that mycobacteria have an unusual lipid metabolism, which enhances their pathogenicity by providing an impervious cell wall that is resistant to macrophage attack, and which lipid metabolism is facilitated by the novel ability of mycobacteria to synthesize and use complex carbohydrates as lipid carriers. The specific carbohydrates are called polymethylpolysaccharides and were discovered and characterized in the laboratory of the applicant. The polymethylpolysaccharides, composed of a 3-0-methylmannose polysaccharide and a 6-0-methylglucose lipopolysaccharide, act as lipid carriers by coiling up around the extended fatty acid chain and forming a water-soluble 1:1 complex with the included lipid. This unusual interaction is due to the inherently hydrophobic nature of the interior of a coiled Alpha 1 greater than 4-glycan, but it is also enhanced by the increase in nonpolar character provided by the methyl ehter groups. The immediate aims of this proposal are (1) to delineate the pathways for biosynthesis and degradation of the 6-0-methylglucose lipopolysaccharide, (2) to define in more detail the nature of the complexation between polymethylpolysaccharide and lipid, (3) to explore approaches to the chemical synthesis of analogs of the polymethylpolysaccharides that may have useful lipid-binding properties, and (4) to investigate the structure, biosynthesis and immunochemistry of a new mycobacterial glycolipid. Part 1 of this proposal will deal with the incorporation of radiolabeled compounds into precursor intermediates of the polysaccharide and with the characterization of products of enzymic degradation of the intact methylglucose polysaccharide; part 2 will involve studies of polysaccharide-lipid complex formation by fast atom bombardment mass spectrometry, by 1H nuclear magnetic resonance, and by X-ray crystallography; part 3 is concerned with chemical modification of amylose to yield oligosaccharides with lipid-binding properties; and part 4 will make use of classical methods of carbohydrate characterization and immunochemistry.
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