Folate biosynthesis is an essential bacterial pathway that is absent in higher animals, and it has been an effective target of antibacterial agents for over 70 years. The sulfonamide drugs inhibit a key enzyme in the pathway, dihydropteroate synthase (DHPS), by acting as non-productive substrate analogs of paminobenzoic acid (pABA). However, the flexible pABA binding site is structurally susceptible to resistance mutations, and the sulfonamides are rapidly becoming therapeutically ineffective. In contrast, the binding site of the second DHPS substrate, pterin-pyrophosphate, is buried in a conserved pocket that is less likely to tolerate mutations. We propose to generate new classes of potent DHPS inhibitors that specifically engage this pocket. These inhibitors have the potential of being developed into novel therapeutic agents that still target folate synthesis but which avoid the problems of resistance. To generate effective inhibitors of any enzyme, it is crucial to understand the structure and mechanism of its active site. This information is largely absent for DHPS, and understanding how DHPS performs catalysis at the molecular level will be a central goal of the application. This comprehensive project will encompass biochemistry, structural biology, medicinal chemistry, computational biology, and microbiology, and will be performed in two laboratories at neighboring institutions in Memphis. The central focus of the project is the design and synthesis of novel small molecules that can be used to probe the DHPS mechanism and also be evaluated as DHPS inhibitors. Promising inhibitor scaffolds will then be tested for their potential as anti-microbials by direct screening of select organisms. The more potent inhibitors will be used to create derivative libraries for further screening and evaluation. The use of state-of-the-art drug discovery software, library synthesis, high-throughput screening and X-ray crystallography are central features of the research. Our goal is to provide a solid platform for the development of new, desperately-needed, broad-spectrum anti-infectives agents. However, we are also focused on developing specific therapies for the category A biowarfare agents B. anthracis, Y. pestis and F. tularensis, as well as for pathogenic protozoa and fungi.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Special Emphasis Panel (ZRG1-IDM-M (03))
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Xu, Zuoyu
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St. Jude Children's Research Hospital
United States
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Griffith, Elizabeth C; Wallace, Miranda J; Wu, Yinan et al. (2018) The Structural and Functional Basis for Recurring Sulfa Drug Resistance Mutations in Staphylococcus aureus Dihydropteroate Synthase. Front Microbiol 9:1369
Zhao, Ying; Shadrick, William R; Wallace, Miranda J et al. (2016) Pterin-sulfa conjugates as dihydropteroate synthase inhibitors and antibacterial agents. Bioorg Med Chem Lett 26:3950-4
Hammoudeh, Dalia I; Daté, Mihir; Yun, Mi-Kyung et al. (2014) Identification and characterization of an allosteric inhibitory site on dihydropteroate synthase. ACS Chem Biol 9:1294-302
Yun, Mi-Kyung; Hoagland, Daniel; Kumar, Gyanendra et al. (2014) The identification, analysis and structure-based development of novel inhibitors of 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase. Bioorg Med Chem 22:2157-65
Hammoudeh, Dalia I; Zhao, Ying; White, Stephen W et al. (2013) Replacing sulfa drugs with novel DHPS inhibitors. Future Med Chem 5:1331-40
Zhao, Ying; Hammoudeh, Dalia; Yun, Mi-Kyung et al. (2012) Structure-based design of novel pyrimido[4,5-c]pyridazine derivatives as dihydropteroate synthase inhibitors with increased affinity. ChemMedChem 7:861-70
Qi, Jianjun; Virga, Kristopher G; Das, Sourav et al. (2011) Synthesis of bi-substrate state mimics of dihydropteroate synthase as potential inhibitors and molecular probes. Bioorg Med Chem 19:1298-305
Zhao, Ying; Hammoudeh, Dalia; Lin, Wenwei et al. (2011) Development of a pterin-based fluorescent probe for screening dihydropteroate synthase. Bioconjug Chem 22:2110-7
Hevener, Kirk E; Yun, Mi-Kyung; Qi, Jianjun et al. (2010) Structural studies of pterin-based inhibitors of dihydropteroate synthase. J Med Chem 53:166-77
Pemble 4th, Charles W; Mehta, Perdeep K; Mehra, Smriti et al. (2010) Crystal structure of the 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase•dihydropteroate synthase bifunctional enzyme from Francisella tularensis. PLoS One 5:e14165

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