FIG. 3.

Fluorescence analysis of the interaction between the modified forms of UMP kinase and UTP. UMP kinase (1 μM in terms of monomer) in 50 mM Tris-HCl (pH 7.4) and 100 mM NaCl was titrated at 332 nm (wild type), 333 nm (R62H and D77N), or 334 nm (D168N) with UTP (between 0.1 and 700 μM). The fluorescence intensity of wild-type UMP kinase in the absence of UTP was considered 100%.