FIGURE 8.

Chemical shift perturbation of cytb₅ resonances upon complex formation with tr-CYP2B4. As with wt-CYP2B4-cytb₅ interactions, CSPs from tr-CYP2B4-cytb₅ are also characterized by the small magnitude and wide dispersion, rendering accurate binding interface mapping impossible but allowing rough estimations of epitopes involved in tr-CYP2B4-cytb₅ interactions. Weighted averages of chemical shift differences (Δδ_avg) for backbone amides of cytb₅ upon interaction with tr-CYP2B4 at a 1:1 molar ratio in a lipid-free solution (A) and solution containing DLPC/DHPC isotropic bicelles (B) are plotted against cytb₅ residue number. The dashed line represents the mean chemical shift change among all residues, and the solid line represents the mean chemical shift change plus one S.D. Residues with Δδ_avg above the solid line are considered to be the most affected among all of the cytb₅ residues upon the addition of tr-CYP2B4. The residues most affected are highlighted in magenta for those located on the front face of cytb₅ around the heme edge and yellow for those not in this area, both on the histogram and in the three-dimensional structures of cytb₅ above each corresponding histogram. The structure of the soluble domain of cytb₅ is shown on the left, and that of the full-length cytb₅ is shown on the right.