For all experiments, fluorescence anisotropy was measured using an EnVision plate reader (PerkinElmer), exciting at 531 nm and detecting polarized emission at 579 nm wavelength. For analyzing data and determining Kd values, Prism (GraphPad) was used for least-square fitting of the measured fluorescence anisotropy values (Y) at different protein concentrations (X) with a single-site binding curve with Hill slope, a nonspecific linear term, and a constant background using the equation \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\rm{Y}}=(({{\rm{Bmax}}}^{\ast }{{\rm{X}}}^{\wedge }{\rm{h}})/({{\rm{Kd}}}^{\wedge }{\rm{h}}+{{\rm{X}}}^{\wedge }{\rm{h}}))+{{\rm{NS}}}^{\ast }{\rm{X}}+{\rm{Background}}$$\end{document}Y=((Bmax⁎X∧h)/(Kd∧h+X∧h))+NS⁎X+Background, where Kd is the equilibrium dissociation constant, h is the Hill coefficient, and Bmax is the extrapolated maximum anisotropy at complete binding.