| | Peptidoglycan is the major structural component of the cell wall and a defining feature of bacteria. It is also the target of many clinically used antibiotics, such as penicillin and other beta-lactams, imipenems, and glycopeptides. Unfortunately, resistance to these and other antibiotics has become widespread and we need new antibiotics to treat resistant infections. This need motivated us to begin to investigate enzymes along the pathway that had not been well characterized. These enzymes include MurG, the enzyme that forms the disaccharide subunit of peptidoglycan, and the bacterial transglycosylases, which polymerize this disaccharide subunit to form the carbohydrate chains of peptidoglycan. Efforts to study MurG and the transglycosylases were hampered for many years because there were no good ways to obtain substrates to monitor enzymatic activity. We developed the first synthetic routes to make substrates for MurG and the transglycosylases, enabling us to study the enzymes and to dissect the mechanisms of various natural product inhibitors. We have made substantial progress towards understanding MurG, determining the kinetic mechanism, obtaining crystal structures with and without substrate bound, and developing a high throughput screen for inhibitors. We are currently working towards understanding the transglycosylases, a large family of enzymes for which there is still no detailed structural or mechanistic information.
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"Bacterial Transglycosylase Inhibitors" Ostash B and Walker* S. Curr Opin Chem Biol 2005;9:459-466.
"Kinetic Characterization of the Glycosyltransferase Module of Stahylococcus aureus PBP2" Barrett D, Leimkuhler C, Chen L, Walker D, Kahne D, Walker* S. J. Bacteriol. 2005;187:2215-2217.
"Crystal Structure of the MurG: UDP-GlcNAc Complex Reveals Common Structural Principles of a Superfamily of Glycosyltransferases" Hu Y, Chen L, Ha S, Gross B, Falcone B, Walker D, Mokhtarzadeh M, Walker S. Proc. Natl. Acad. Sci. USA 2003; 100:845-849.
"Intrinsic Lipid Preferences and Kinetic Mechanism of Escherichia coli MurG" Chen L, Men H, Ha S, Ye X-Y, Brunner L, Hu Y, and Walker S. Biochemistry, 2002; 41:6824-6833.
"Better Substrates for Bacterial Transglycosylases" Ye X-Y, Lo M, Brunner L, Walker D, Kahne D, Walker S. J. Am. Chem. Soc. 2001;123:3155-3116.
"The 1.9 Å crystal structure of E. coli MurG, a membrane-associated glycosyltransferase involved in peptidoglycan biosynthesis" Ha S, Walker D, Shi Y, Walker S. Protein Science 2000;9:1045-1052.
"Substrate Synthesis and Activity Assay for MurG" Men H, Park P, Ge M, Walker S. J. Am. Chem. Soc. 1998;120:2484-2485.
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