1887

Abstract

Entry of methotrexate (MTX) into the folate prototrophic bacterium was poorly inhibited by folate or its natural derivative folinic acid, suggesting that if MTX is transported via a folate transporter, the affinity of that transporter for MTX is higher than for folate. In the range of concentrations tested, MTX uptake was non-concentrative and decreased in ATP-depleted bacteria. When the external concentration of MTX was increased from 1 × 10 to 1 × 10 , uptake became saturated and was insensitive to ionophores. However when external MTX concentrations were increased to 1 × 10 , uptake increased linearly, and was inhibited by the ionophores carbonyl cyanide -chlorophenylhydrazone (CCCP) and valinomycin, suggesting that the process was energized by the protonmotive force (Δ) at this concentration. A model for MTX entry in . is proposed with respect to these results. The high level of resistance to MTX of the nonsense mutant cannot be entirely explained by a decrease in MTX uptake.

Loading

Article metrics loading...

/content/journal/micro/10.1099/00221287-131-6-1273
1985-06-01
2022-01-20
Loading full text...

Full text loading...

/deliver/fulltext/micro/131/6/mic-131-6-1273.html?itemId=/content/journal/micro/10.1099/00221287-131-6-1273&mimeType=html&fmt=ahah

References

  1. Blakley R. L. 1969; Biochemistry and pharmacology of folate analogues. In The Biochemistry of Folic Acid and Related Pteridines464–517 New York: American Elsevier;
    [Google Scholar]
  2. Cooper B. A. 1970; Studies of [3H]folic acid uptake by Lactobacillus casei . Biochimica et biophysica acta 208:99–109
    [Google Scholar]
  3. Ephrussi-Taylor H., Sicard A. M., Kamen R. 1965; Genetic recombination in DNA-induced transformation of pneumococcus. I. The problem of relative efficiency of transforming factors. Genetics 51:455–475
    [Google Scholar]
  4. Friedman L. R., Ravin A. W. 1972; Genetic and biochemical properties of thymidine-dependent mutants of pneumococcus. Journal of Bacteriology 109:459–461
    [Google Scholar]
  5. Gasc A. M., Vacher J., Buckingham R., Sicard A. M. 1979; Characterization of an amber suppressor in pneumococcus. Molecular and General Genetics 172:295–301
    [Google Scholar]
  6. Goldman D., Lichenstein N. S., Oliverio V. T. 1968; Carrier-mediated transport of the folic acid analogue methotrexate in the LI210 leukemia cell. Journal of Biological Chemistry 243:5007–5017
    [Google Scholar]
  7. Harold F. M. 1977; Membranes and energy transduction in bacteria. Current Topics in Bioenergetics 6:83–149
    [Google Scholar]
  8. Henderson G. B., Huennekens F. M. 1974; Transport of folate compounds into Lactobacillus casei . Archives of Biochemistry and Biophysics 164:722–728
    [Google Scholar]
  9. Huennekens F. M., Vitols K. S., Henderson G. B. 1978; Transport of folate compounds in bacterial and mammalian cells. Advances in Enzymology 47:313–346
    [Google Scholar]
  10. Sicard A. M. 1964; A new synthetic medium for Diplococcus pneumoniae and its use for the study of reciprocal transformation at the amiA locus. Genetics 50:31–44
    [Google Scholar]
  11. Sirotnak F. M., Donati G. J., Hutchison D. J. 1964; Genetic modification of the structure and amount of FH2 reductase in amethopterin resistant Diplococcus pneumoniae . Journal of Biological Chemistry 239:4298–4302
    [Google Scholar]
  12. Sirotnak F. M., Sargent M. G., Hutchison D. J. 1967a; Genetically alterable transport of amethopterin in Diplococcus pneumoniae I. Physiological properties and kinetics of the wild-type system. Journal of Bacteriology 93:309–314
    [Google Scholar]
  13. Sirotnak F. M., Sargent M. G., Hutchison D. J. 1967b; Genetically alterable transport of amethopterin in Diplococcus pneumoniae II. Impairment of the system associated with various mutant genotypes. Journal of Bacteriology 93:315–319
    [Google Scholar]
  14. Tiraby G., Fox M. S., Bernheimer H. 1975; Marker discrimination in deoxyribonucleic acid mediated transformation of various pneumococcus strains. Journal of Bacteriology 121:608–618
    [Google Scholar]
  15. Trombe M. C. 1972; Caracterisation de mutants de resistance à l’améthoptérine chez Streptococcus pneumoniae. Alteration du potentiel transmembranaire. Mise en evidence d’une cible membranaire pour l’améthoptérine. PhD. thesis Université Paul Sabatier; Toulouse, France:
    [Google Scholar]
  16. Trombe M. G., Sicard A. M. 1973; Analyse phénotypique et génétique de mutants de resistance à l’améthoptérine présentant une alteration du système de transport de l’antimétabolite. Compie rendu hebdonadaire des séances de l’Acadèmie des sciences 276, sèrie D3495–3498
    [Google Scholar]
  17. Trombe M. C., Sicard A. M. 1975; Dihydrofolate reductase from the wild type and aminopterin-resistant mutants of Diplococcus pneumoniae . Journal of Bacteriology 121:608–618
    [Google Scholar]
  18. Trombe M. C., Laneelle M. A., Laneelle G. 1979; Lipid composition of aminopterin-resistant and sensitive strains of Streptococcus pneumoniae Effect of aminopterin inhibition. Biochimica et biophysica acta 574:290–300
    [Google Scholar]
  19. Trombe M. C., Laneelle G., Sicard A. M. 1984; Characterization of a Streptococcus pneumoniae mutant with altered electric transmembrane potential. Journal of Bacteriology 158:1109–1114
    [Google Scholar]
http://instance.metastore.ingenta.com/content/journal/micro/10.1099/00221287-131-6-1273
Loading
/content/journal/micro/10.1099/00221287-131-6-1273
Loading

Data & Media loading...

Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error