FIGURE 4.

A and B, normalized change in fluorescence for Ca²⁺-binding titrations for P40A Rv (A) and C39D Rv (B). Equation 2 was used to fit the titration data. The dashed lines are for WT Rv (from Fig. 2A). C, pulldown assay in which RGS was first immobilized on a Ni-NTA matrix, WT, C39D, or P40A Rv added in the presence of 1 mm CaCl₂, and finally the RGS-Rv complex eluted with 250 mm imidazole. Lanes are defined as L, load; FT, flow-through; W, last wash; E, imidazole elution.