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Thermodynamic analysis of the binding of 5-fluoro-2'-deoxyuridine 5'-monophosphate to thymidylate synthase over a range of temperatures

García Fuentes, Luis and Reche, Pedro A and López Mayorga, O and Santi, D V and González-Pacanowska, D. and Barón, C (1995) Thermodynamic analysis of the binding of 5-fluoro-2'-deoxyuridine 5'-monophosphate to thymidylate synthase over a range of temperatures. European Journal of Biochemistry / FEBS, 232 (2). pp. 641-5. ISSN 0014-2956

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Abstract

The binding of 5-fluoro-2'-deoxyuridine 5'-monophosphate (FdUMP) to Lactobacillus casei recombinant thymidylate synthase has been studied by isothermal titration microcalorimetry at pH 7.1 over the temperature range 16-35 degrees C. Calorimetric measurements in various buffer systems with different heats of ionization suggest that a proton uptake is involved in the binding process of the nucleotide. In the temperature range investigated, the mol protons bound/mol nucleotide increases as the temperature decreases. A model of two equal and independent sites fits well with the binding isotherms for thymidylate synthase. The binding constants, the changes in Gibbs energy, enthalpy, and entropy/site for FdUMP binding were calculated at each temperature. The results show that the binding is driven by both enthalpy and entropy contributions in the range 16-35 degrees C. The enthalpy changes become more negative as the temperature increases, with delta Cp = -170 +/- 20 J.K-1.(mol FdUMP bound)-1. The behavior of the system supports the observation that FdUMP binds to thymidylate synthase without producing profound conformational changes in the protein dimer.


Item Type:Article
Uncontrolled Keywords:Thymidylate synthase; 5-fluoro-2'-deoxyuridine 5'; Monophosphate; Microcalorimetry; Binding
Subjects:Sciences > Chemistry > Molecular biology
Sciences > Chemistry > Biochemistry
ID Code:9354
Deposited On:14 Aug 2009 10:56
Last Modified:01 Sep 2010 10:57

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