Temperature Modulation of the DBDp53 Structure as Monitored by Static and Time-Resolved Fluorescence Combined with Molecular Dynamics Simulations.

Trp146 of the p53 DNA-binding domain (DBD) was investigated by static and time-resolved fluorescence combined with molecular dynamics (MD) simulations at different temperatures (25, 30, 37, and 45 °C). Static emission spectra exhibit an intensity maximum at 30 °C without any substantial peak shift, while the time-resolved fluorescence displays a peculiar stretched exponential decay, indicative of a structural disorder, at all of the investigated temperatures. The stretched exponential parameter was found to increase at 37 °C. An analysis of the MD simulation trajectories evidenced the occurrence of jumps in the temporal evolution of the distances between Trp146 and residues Arg110, Asp228, Cys229, and Gln144, which are mainly responsible for Trp146 fluorescence quenching. The times that these quenchers spend close to or far from Trp146 can provide an explanation for the static fluorescence behavior. Further essential dynamics analysis of the MD trajectories indicates a significant restriction of protein global motions above 37 °C. These results are consistent with a decrease in the structural heterogeneity of DBD as the temperature increases. The results are also discussed in view of understanding how temperature can modulate the p53 capability to binding partners, including DNA.