Role of Conformational Changes of Hexameric Bacterial Uridine Phosphorylases in Substrate Binding

Crystals of mutants of uridine phosphorylase from Shewanella oneidensis MR-1 at the active-site threonine residue were obtained, and the three-dimensional structures of the mutants were determined. It was shown that the loop 161–179 responsible for the nucleoside recognition is involved in stabilization of the hexameric structure of the protein and its disorder significantly facilitates the access of nucleoside to the enzyme active site. The role of conformational changes in the enzyme function is discussed.