Structural investigation of the thymidine phosphorylase from Salmonella typhimurium in the unliganded state and its complexes with thymidine and uridine

Molecular Dynamics Study of Escherichia coli Thymidine Phosphorylase in a Complex with 3'-Azidothymidine Inhibitor and Phosphate

Abstract—

Using a molecular dynamics method, the state of the dimeric thymidine phosphorylase molecule from Escherichia coli in a complex with noncompetitive enzyme inhibitor 3'-azidothymidine and phosphate ion was studied on a trajectory of 50 ns. Previously obtained atomic coordinates of a complex of thymidine phosphorylase with azidothymidine and sulfate at a resolution of 1.52 Å were used as a starting model. It was demonstrated that both subunits of a dimeric enzyme molecule function asynchronously in a given time interval; moreover, each subunit maintains an open conformation. It was found that the nature of ligand at the nucleoside center affects the binding strength of phosphate in the phosphate center. In a complex with an inhibitor, both ligands over the entire time interval remain bound to the enzyme, while the release of phosphate from the active center is observed when simulating the behavior of thymidine phosphorylase in the presence of phosphate and thymidine substrate. The stabilizing effect of azidothymidine on phosphate binding is consistent with the behavior of azidothymidine as a noncompetitive inhibitor of thymidine phosphorylase.

Crystal structure of pyrimidine-nucleoside phosphorylase from Bacillus subtilis in complex with imidazole and sulfate

Pyrimidine-nucleoside phosphorylase catalyzes the phosphorolytic cleavage of thymidine and uridine with equal activity. Investigation of this protein is essential for anticancer drug design. Here, the structure of this protein from Bacillus subtilis in complex with imidazole and sulfate is reported at 1.9 Å resolution, which is an improvement on the previously reported structure at 2.6 Å resolution. The localization and position of imidazole in the nucleoside-binding site reflects the possible binding of ligands that possess an imidazole ring.