N-Glycosidically-linked glycoproteins are found in many mammalian cells, such as aortic smooth muscle cells and these complex carbohydrates play key roles in various recognition phenomena. The biosynthesis of the carbohydrate portion of these proteins involves the participation of lipid-linked saccharide intermediates. While the general pathway of synthesis of these intermediates is known, there is relatively little information available about the details of the individual reactions. In this study, we will try two different approaches to delineate the individual reactions involved in the assembly of the lipid-linked oligosaccharides. In the first approach, we will look for antibiotics, or other inhibitors, which block the lipid-linked saccharide pathway at different points. We hope that these inhibitors will allow us to stop the series of reactions at different steps and thus allow the accumulation of intermediates prior to the block. These intermediates can be characterized and used as substrates in other reactions to examine individual glycosyl transferases. In the second approach, we will solubilize and purify the enzymes involved in the assembly of lipid-linked saccharides so that the individual enzymes can be studied. We hope to be able to do this in a sequential fashion so that the product of one enzymatic reaction can be used as a substrate for the next transferase. We will also study this pathway to determine how it is regulated and what types of controls exist to inhibit or activate it. In terms of functional aspects of the glycoproteins we will study the role of the carbohydrate in the human serum lipoproteins. For example, we will ask whether the absence of the oligosaccharide chain of low density lipoprotein has any effect on secretion of this glycoprotein or on its binding to heparin. We will also study the interaction of LDL with the cell surface receptor and the binding of bacteria to mammalian cells.
NIH ExPorter
NIH ExPorter