FIGURE 5.

Pairs of sites selected for site-directed spin labeling in the CBD1 domain of CBD12 and their corresponding DEER spectra. The ribbon diagram of CBD1 is shown in purple in the left panel (coordinates were from PDB 2DPK). The sites where pairs of R1 spin labeled side chains were incorporated are shown as solid spheres connected by dashed lines. The spheres are centered at the coordinates of the β-carbon of each selected residue. The positions of the four Ca²⁺-binding sites are shown as small yellow spheres. The DEER data for each of the five pairs of sites are shown as solid black lines in the right panel. The fits to the DEER data are shown as solid blue lines (no bound Ca²⁺) and solid red lines (saturating level of bound Ca²⁺). The average distances and widths of the distance distributions are shown in the insets to each DEER data set in Å.