title: Pyrimidine Pathway-Dependent and -Independent Functions of the Toxoplasma gondii Mitochondrial Dihydroorotate Dehydrogenase.
abstract: Dihydroorotate dehydrogenase (DHODH) mediates the fourth step of de novo pyrimidine biosynthesis and is a proven drug target for inducing immunosuppression in therapy of human disease as well as a rapidly emerging drug target for treatment of malaria. In Toxoplasma gondii, disruption of the first, fifth, or sixth step of de novo pyrimidine biosynthesis induced uracil auxotrophy. However, previous attempts to generate uracil auxotrophy by genetically deleting the mitochondrion-associated DHODH of T. gondii (TgDHODH) failed. To further address the essentiality of TgDHODH, mutant gene alleles deficient in TgDHODH activity were designed to ablate the enzyme activity. Replacement of the endogenous DHODH gene with catalytically deficient DHODH gene alleles induced uracil auxotrophy. Catalytically deficient TgDHODH localized to the mitochondria, and parasites retained mitochondrial membrane potential. These results show that TgDHODH is essential for the synthesis of pyrimidines and suggest that TgDHODH is required for a second essential function independent of its role in pyrimidine biosynthesis.
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA.
authors.forename: Miryam Andrea
authors.initials: MA
authors.lastname: Hortua Triana
authors.affiliation: Departamento de Ciencias Biológicas, Universidad de los Andes, Bogotá, Colombia.
authors.forename: Daniela
authors.initials: D
authors.lastname: Cajiao Herrera
authors.affiliation: Departamento de Ciencias Biológicas, Universidad de los Andes, Bogotá, Colombia.
authors.forename: Barbara H
authors.initials: BH
authors.lastname: Zimmermann
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA.
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Fox
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA david.j.bzik@dartmouth.edu.
authors.forename: David J
authors.initials: DJ
authors.lastname: Bzik
mesh_terms: D053898:Biosynthetic Pathways; D000090722:Dihydroorotate Dehydrogenase; D005347:Fibroblasts / Q000378:metabolism / Q000469:parasitology; D055786:Gene Knockout Techniques; D006801:Humans; D008928:Mitochondria / Q000201:enzymology*; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011743:Pyrimidines / Q000096:biosynthesis*; D014122:Toxoplasma / Q000201:enzymology*; D014123:Toxoplasmosis / Q000378:metabolism*; D014498:Uracil / Q000378:metabolism
chemical_list: D000090722:Dihydroorotate Dehydrogenase; D011743:Pyrimidines; D014498:Uracil; D044925:Oxidoreductases Acting on CH-CH Group Donors