Fluorescence emission intensity of the ABC fragment plotted versus the concentration of the DEFG fragment (A) and that of the ABCDE fragment versus the concentration of the FG fragment (B). In A, the solution contained a 0.5-μM ABC fragment, 1 M urea, and 750 mM glycerol. In B, the ABCDE fragment concentration was 1 μM, and the solution did not contain urea or glycerol. (C) Urea dependence of the dissociation constant of the reconstitution reaction of the ABC and DEFG fragments. Data with 750 mM glycerol are shown. (D) Glycerol dependence of the dissociation constant of the reconstitution reaction of the ABC and DEFG fragments. Data in the presence of 2 M urea are shown.