Information de reference pour ce titreAccession Number: | 01244637-199810000-00024.
|
Author: | Jarvis, Simon M; de Koning, Harry P
|
Title: | A highly selective, high-affinity transporter for uracil in Trypanosoma brucei brucei: evidence for proton-dependent transport.[Article]
|
Source: | Biochemistry & Cell Biology. 76(5):853-858, October 1998.
|
Abstract: | The presence of an uptake mechanism for uracil in procyclic forms of the protozoan parasite Trypanosoma brucei brucei was investigated. Uptake of [3H]uracil at 22[degrees]C was rapid and saturable and appeared to be mediated by a single high-affinity transporter, designated U1, with an apparent Km of 0.46 +/- 0.09 [mu]M and a Vmax of 0.65 +/- 0.08 pmol[middle dot](107 cells)-1[middle dot]s-1. [3H]Uracil uptake was not inhibited by a broad range of purine and pyrimidine nucleosides and nucleobases (concentrations up to 1 mM), with the exception of uridine, which acted as an apparent weak inhibitor (Ki value of 48 +/- 15 [mu]M). Similarly, most chemical analogues of uracil, such as 5-chlorouracil, 3-deazauracil, and 2-thiouracil, had little or no affinity for the U1 carrier. Only 5-fluorouracil was found to be a relatively potent inhibitor of uracil uptake (Ki = 3.2 +/- 0.4 [mu]M). Transport of uracil was independent of extracellular sodium and potassium gradients, as replacement of NaCl in the assay buffer by N-methyl-D-glucamine, KCl, LiCl, CsCl, or RbCl did not affect initial rates of transport. However, the proton ionophore carbonyl cyanide chlorophenylhydrazone inhibited up to 70% of [3H]uracil flux. These data show that uracil uptake in T. b. brucei procyclics is mediated by a single high-affinity transporter with high substrate selectivity and are consistent with a nucleobase-H+-symporter model for this carrier.
(C) 1998 National Research Council Canada
|
Author Keywords: | uracil; trypanosome; proton-nucleobase cotransport; nucleobase transport; uracile; trypanosome; cotransport proton-base azotee; transport de bases azotees.
|
References: | Brun, R., and Schonenberger, M. 1979. Cultivation and in vivo cloning of procyclic culture forms of Trypanosoma brucei in a semi-defined medium. Acta Trop. 36: 289-292.
Burton, K. 1977. Transport of adenine, hypoxanthine and uracil into Escherichia coli. Biochem. J. 168: 195-204.
Burton, K. 1983. Transport of nucleic acid bases into Escherichia coli. J. Gen. Microbiol. 129: 3505-3513.
Carter, N.S., and Fairlamb, A.H. 1993. Arsenical-resistant trypanosomes lack an unusual adenosine transporter. Nature (London), 361: 173-175.
De Koning, H.P., and Jarvis, S.M. 1997a. Hypoxanthine uptake through a purine-selective nucleobase transporter in Trypanosoma brucei brucei procyclic cells is driven by protonmotive force. Eur. J. Biochem. 247: 1102-1110.
De Koning, H.P., and Jarvis, S.M. 1997b. Purine nucleobase transport in bloodstream forms of Trypanosoma brucei brucei is mediated by two novel transporters. Mol. Biochem. Parasitol. 89: 245-258.
De Koning, H.P., Watson, C.J., and Jarvis, S.M. 1998. Characterization of a nucleoside/proton symporter in procyclic Trypanosoma brucei brucei. J. Biol. Chem. 273: 9486-9494.
Domin, B.A., Mahoney, W.B., and Zimmerman, T.P. 1993. Transport of 5-fluorouracil and uracil into human erythrocytes. Biochem. Pharmacol. 46: 503-510.
Eddy, A.A. 1982. Mechanisms of solute transport in selected eukaryotic microorganisms. Adv. Microb. Physiol. 23: 1-78.
Griffith, D.A., and Jarvis, S.M 1994. Characterization of a sodium-dependent concentrative nucleobase-transport system in guinea-pig kidney cortex brush-border membrane vesicles. Biochem. J. 303: 901-905.
Griffith, D.A., and Jarvis, S.M 1996. Nucleoside and nucleobase transport systems of mammalian cells. Biochim. Biophys. Acta, 1286: 153-181.
Gutteridge, W.E., and Coombs, G.H. 1977. Biochemistry of parasitic protozoa. MacMillan Press, London.
Hammond, D.J., and Gutteridge, W.E. 1984. Purine and pyrimidine metabolism in the trypanosomatidae. Mol. Biochem. Parasitol. 13: 243-261.
Hassan, H.F., and Coombs, G.H. 1988. Purine and pyrimidine metabolism in parasitic protozoa. FEMS Microbiol. Rev. 54: 47-84.
Hopkins, P., Chevallier, N.R., Jund, R., and Eddy, A.A. 1988. Use of plasmid vectors to show that the uracil and cytosine permeases of the yeast Saccharomyces cerevisiae are electro genic proton symports. FEMS Microbiol. Lett. 49: 173-177.
Rubin, R.J., Jaffe, J.J., and Handschumacher, R.E. 1962. Quantitative differences in the pyrimidine metabolism of Trypanosoma equiperdum and mammals as characterized by 6-azauracil and 6-azauridine. Biochem. Pharmacol. 11: 563-572.
Wang, C.C. 1983. Purine and pyrimidine metabolism in Tricho monadae and Giardia: potential targets for chemotherapy. In Biochemical basis of drug action. Edited by T.P. Singer, T. Mansour, and R. Ondarza. Academic Press, New York. pp. 133-145.
Washington, C.B., and Giacomini, K.M. 1995. Mechanisms of nucleobase transport in rabbit choroid plexus; evidence for a Na+-dependent nucleobase transporter with broad substrate selectivity. J. Biol. Chem. 270: 22 816-22 819.
Yuasa, H., Matsuhisa, E., and Watanabe, J. 1996. Intestinal brush border transport mechanism of 5-fluorouracil in rats. Biol. Pharm. Bull. 19: 94-99.
|
Language: | English.
|
Document Type: | Article: PDF Only.
|
Journal Subset: | Life Sciences.
|
ISSN: | 1208-6002
|
Annotation(s) | |
|
|