“…Danenberg and Danenberg (1979) have shown that FdUMP and CHrlLfolate binding to one catalytic site induced conformational changes that exposed the other catalytic site. Also, the formation of the ternary complex of thymidylate synthase with FdUMP and CH2-H4folate produced changes in the hydrodynamic properties of the enzyme, as measured by gel filtration and density gradient centrifugation, that were consistent with large conformational changes resulting in a more compact structure (Lockshin & Danenberg, 1980). The changes in absorption, fluorescence, and circular dichroic spectra that accompany ternary complex formation are consistent with conformational changes, though other interpretations are possible (Danenberg et al, 1974;Santi et al, 1974;Galivan et al, 1975;Donato et al, 1976; Manavalan et al, 1986).…”