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Interaction of dihydrofolate reductase with methotrexate: ensemble and single-molecule kinetics.

Publication ,  Journal Article
Rajagopalan, PTR; Zhang, Z; McCourt, L; Dwyer, M; Benkovic, SJ; Hammes, GG
Published in: Proc Natl Acad Sci U S A
October 15, 2002

The thermodynamics and kinetics of the interaction of dihydrofolate reductase (DHFR) with methotrexate have been studied by using fluorescence, stopped-flow, and single-molecule methods. DHFR was modified to permit the covalent addition of a fluorescent molecule, Alexa 488, and a biotin at the N terminus of the molecule. The fluorescent molecule was placed on a protein loop that closes over methotrexate when binding occurs, thus causing a quenching of the fluorescence. The biotin was used to attach the enzyme in an active form to a glass surface for single-molecule studies. The equilibrium dissociation constant for the binding of methotrexate to the enzyme is 9.5 nM. The stopped-flow studies revealed that methotrexate binds to two different conformations of the enzyme, and the association and dissociation rate constants were determined. The single-molecule investigation revealed a conformational change in the enzyme-methotrexate complex that was not observed in the stopped-flow studies. The ensemble averaged rate constants for this conformation change in both directions is about 2-4 s(-1) and is attributed to the opening and closing of the enzyme loop over the bound methotrexate. Thus the mechanism of methotrexate binding to DHFR involves multiple steps and protein conformational changes.

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Published In

Proc Natl Acad Sci U S A

DOI

ISSN

0027-8424

Publication Date

October 15, 2002

Volume

99

Issue

21

Start / End Page

13481 / 13486

Location

United States

Related Subject Headings

  • Thermodynamics
  • Tetrahydrofolate Dehydrogenase
  • Protein Conformation
  • Mutation
  • Models, Molecular
  • Microscopy, Fluorescence
  • Methotrexate
  • Kinetics
  • Genes, Bacterial
  • Fluorescent Dyes
 

Citation

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Rajagopalan, P. T. R., Zhang, Z., McCourt, L., Dwyer, M., Benkovic, S. J., & Hammes, G. G. (2002). Interaction of dihydrofolate reductase with methotrexate: ensemble and single-molecule kinetics. Proc Natl Acad Sci U S A, 99(21), 13481–13486. https://doi.org/10.1073/pnas.172501499
Rajagopalan, PT Ravi, Zhiquan Zhang, Lynn McCourt, Mary Dwyer, Stephen J. Benkovic, and Gordon G. Hammes. “Interaction of dihydrofolate reductase with methotrexate: ensemble and single-molecule kinetics.Proc Natl Acad Sci U S A 99, no. 21 (October 15, 2002): 13481–86. https://doi.org/10.1073/pnas.172501499.
Rajagopalan PTR, Zhang Z, McCourt L, Dwyer M, Benkovic SJ, Hammes GG. Interaction of dihydrofolate reductase with methotrexate: ensemble and single-molecule kinetics. Proc Natl Acad Sci U S A. 2002 Oct 15;99(21):13481–6.
Rajagopalan, PT Ravi, et al. “Interaction of dihydrofolate reductase with methotrexate: ensemble and single-molecule kinetics.Proc Natl Acad Sci U S A, vol. 99, no. 21, Oct. 2002, pp. 13481–86. Pubmed, doi:10.1073/pnas.172501499.
Rajagopalan PTR, Zhang Z, McCourt L, Dwyer M, Benkovic SJ, Hammes GG. Interaction of dihydrofolate reductase with methotrexate: ensemble and single-molecule kinetics. Proc Natl Acad Sci U S A. 2002 Oct 15;99(21):13481–13486.
Journal cover image

Published In

Proc Natl Acad Sci U S A

DOI

ISSN

0027-8424

Publication Date

October 15, 2002

Volume

99

Issue

21

Start / End Page

13481 / 13486

Location

United States

Related Subject Headings

  • Thermodynamics
  • Tetrahydrofolate Dehydrogenase
  • Protein Conformation
  • Mutation
  • Models, Molecular
  • Microscopy, Fluorescence
  • Methotrexate
  • Kinetics
  • Genes, Bacterial
  • Fluorescent Dyes