C. Yuan et al., Association and activation of fructose 1,6-bisphosphase during unfolding and refolding: Spectroscopic and enzymatic studies, J PROTEIN C, 20(1), 2001, pp. 39-47
Fructose 1,6-biphosphase is a well-characterized oligomer enzyme, and many
effectors allosterically control its activity. In this report, we compared
the activity, allosteric properties, and conformational changes in its dena
turant-induced unfolding processes. In addition, a trpytophan residue has b
een introduced into the interface between the C1 and C2 subunits to investi
gate conformational changes during unfolding. Results show that the denatur
ation curves of WT FruP(2)ase detected by various methods do not agree, and
the dissociation occurs first with a monomeric form existing around 0.4 M
GdmCl as shown by gel filtration. The dissociation of all mutants is accomp
anied by changes in fluorescence intensity. The results suggest that the un
folding of FruP(2)ase is a complicated, multiphase process. The activation
of FruP(2)ase by GdmCl at low concentrations can be interpreted as a conseq
uence of the effect of monovalent cation. In the refolding experiments, it
is found that Mg2+ is not only essential for enzyme activity, but also can
assist the enzyme in refolding and association by preventing the formation
of aggregates.