Figure 6. The binding pocket of the Dvl PDZ domain can be occupied by its intrinsic C-terminus.
(A) Schematic representation of protein constructs mC1 (residues 251–695) and mC1-CΔ7 (residues 251–688) numbered according to the mouse Dvl-1 protein sequence. (B) Polarization change of the fluorescence-labeled peptide Rox-DprC (Rox-SGSLKLMTTV, derived from the C-terminus of Dpr) after addition of mC1-CΔ7 and mC1 proteins in 50 mM phosphate with 0.3 M NaCl and 6 mM β-mercaptoethanol. For the binding of Rox-DprC to mC1, KD is 3.8 ± 0.5 μM the value was obtained by fitting the titration data with the equation: ΔmP = ΔmPmax × [P]/([P] + KD), where ΔmP is the polarization change of Rox-DprC, [P] is the concentration of protein, and both KD and ΔmPmax are the fitting variables. For the binding of Rox-DprC to mC1-CΔ7, KD was estimated as 68 ± 5 μM. Because of the limitation in the titration study, to estimate the KD value, although we used the same equation to fit the titration data, in the fitting, Kd was the only variable and the maximum polarization change, ΔmPmax, was fixed to the value that was obtained in the titration study of Rox-DprC binds to mC1-CΔ7.