Nucleotide Binding to Trimeric dUTPase: Studies on Recombinant Enzymes using Kinetic and Spectroscopic Methods

Research output: ThesisDoctoral Thesis (compilation)

Abstract

Recombinant dUTPase from the bacterium Escherichia coli, the retrovirus equine infectious anemia virus (EIAV) and Homo sapiens have been made available for physico-chemical characterisation. The protocols developed have also proven to be suitable for production of enzymes modified by isotope labelling or other methods. The improved accessibility of enzyme material has enabled the subsequent investigations presented in this thesis and elsewhere. Studies on EIAV dUTPase have assessed rate constants of ligand binding and catalysis, and provided new knowledge concerning the early phase of the catalytic reaction: the substrate binds with diffusion controlled rate (10<sup>8</sup> M<sup>-1</sup>s<sup>-1</sup>) through a simple one-step mechanism. The C-terminal part of dUTPase, which contains similarities to phosphate-binding sequence motifs, is disordered in most crystal structures of the enzyme. This part of the viral enzyme is not involved in the substrate binding step. The dynamics of the C-terminus of the dUTPases from E. coli and EIAV were studied by NMR. The measurements showed a drastic reduction in flexibility upon binding of a substrate analogue to E. coli dUTPase. However, motion of the C-terminal "arm" of EIAV dUTPase could not be detected, possibly due to the rate of motion being below the NMR time range. Another method is needed if this difference between the two enzymes is to be clarified. Comparative studies of the kinetics of the three enzymes (E. coli, human and EIAV dUTPase) revealed that the viral enzyme is as efficient as the other dUTPases in hydrolysing the natural substrate dUTP. The similarities between the viral, bacterial and mammalian enzymes also include low values for <i>K<sub>M</sub></i> (0.1-1.1 µM) for dUTP and strict Michaelis-Menten kinetics. The EIAV dUTPase is less discriminatory than the cellular E. coli and human dUTPases against the related nucleotide dTTP. The binding of other nucleotides is also stronger relative to the affinity for the substrate. Some of the differences in binding strength could be attributed to structural differences between the enzymes.

Details

Authors
  • Johan Nord
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Biological Sciences

Keywords

  • C-terminus, dUTPase, EIAV, Escherichia coli, flexibility, Homo sapiens, kinetics, NMR, nucleotide metabolism, rate constants of lig-and binding, production of recombinant enzyme, dUTP, specificity, Biochemistry, Metabolism, Biokemi
Original languageEnglish
QualificationDoctor
Awarding Institution
Supervisors/Advisors
  • [unknown], [unknown], Supervisor, External person
Award date2000 May 26
Publisher
  • Johan Nord, Department of Biochemistry, Center for Chemistry and Chemical Engineering, P.O. Box 124, S-221 00, Lund, Sweden
Print ISBNs91-628-4133-5
StatePublished - 2000

Bibliographic note

Defence details Date: 2000-05-26 Time: 13:15 Place: Hall B, Center for Chemistry and Chemical Engineering, Lund External reviewer(s) Name: Jonsson, Bengt-Harald Title: Docent Affiliation: Department of Chemistry, Umeå university, Sweden ---

Related research output

Nord, J., Kiefer, M., Adolph, H-W., Zeppezauer, M. M. & Nyman, P-O. 2000 In : FEBS Letters. 472, 2-3, p. 312-316

Research output: Contribution to journalArticle

Nord, J., Larsson, G., Kvassman, J-O., Rosengren, A. M. & Nyman, P-O. 1997 In : FEBS Letters. 414, 2, p. 271-274

Research output: Contribution to journalArticle

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