title: Nutritional requirements of wild-type and folate transport-deficient Leishmania donovani for pterins and folates.
abstract: The nutritional requirements for folates and pterins were assessed for two strains of Leishmania donovani promastigotes, a wild-type (D1700) parental strain and a mutant derivative (MTXA5) which possesses a markedly diminished capacity to transport both [3H]folate and [3H]methotrexate (MTX). Both L. donovani strains have an absolute growth requirement for an exogenous pterin, since their proliferation could not be sustained in completely defined medium lacking either a pterin or a folate. Supplementation of the growth medium by many of a spectrum of folates and pterins could support growth of the wild-type cell line. Surprisingly, however, the MTXA5 strain could not thrive in folate-deficient medium fortified with any of the pterins that promoted wild-type cell division, including biopterin and neopterin. The relationship between the incapacity of MTXA5 cells to transport folate and methotrexate and their inability to multiply in folate-deficient medium supplemented with pterins was evaluated using genetic approaches. First, an independently generated MTX-resistant mutant, MTXB4, was isolated in 1 mM MTX. The phenotype of the MTXB4 cells was like that of MTXA5 cells since they were unable to transport [3H]MTX and [3H]folate or grow in folate-deficient medium supplemented with pterins. Second, three revertants of the MTXA5 cells were selected for their ability to grow in 1 microM biopterin. All three revertants had regained [3H]folate and [3H]MTX transport capability concomitant with growth sensitivity to methotrexate toxicity. These observations provide genetic evidence that the competence of L. donovani to transport [3H]folate and [3H]MTX and the capability of the organisms to utilize pterins as a nutritional factor are influenced by a common genetic locus.
authors.affiliation: Department of Biochemistry and Molecular Biology, Oregon Health Sciences University, Portland 97201.
authors.forename: J T
authors.initials: JT
authors.lastname: Beck
authors.forename: B
authors.initials: B
authors.lastname: Ullman
mesh_terms: D000345:Affinity Labels; D000818:Animals; D001692:Biological Transport; D001708:Biopterins / Q000031:analogs & derivatives / Q000494:pharmacology; D005492:Folic Acid / Q000378:metabolism*; D007700:Kinetics; D007893:Leishmania donovani / Q000254:growth & development / Q000378:metabolism*; D008727:Methotrexate / Q000378:metabolism; D019798:Neopterin; D010641:Phenotype; D011622:Pterins / Q000378:metabolism*
chemical_list: D000345:Affinity Labels; D011622:Pterins; D001708:Biopterins; D019798:Neopterin; D005492:Folic Acid; D008727:Methotrexate