%0 Journal Article
%A García Fuentes, Luis
%A Reche, Pedro A
%A López Mayorga, O
%A Santi, D V
%A González-Pacanowska, D.
%A Barón, C
%T Thermodynamic analysis of the binding of 5-fluoro-2'-deoxyuridine 5'-monophosphate to thymidylate synthase over a range of temperatures
%D 1995
%@ 0014-2956
%U https://hdl.handle.net/20.500.14352/58261
%X 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.
%~