The fluorescence anisotropy of a CPI-motif-containing peptide with a fluorescent label, bound to CP, is plotted vs the total concentration of unlabeled CBR115 (black) or CBR71 (red). The points represent data values from experiments in duplicate, and the lines are the best fits to a competition model with 1:1 stoichiometry. The concentration of CP was 50 nM, and the concentration of the CPI-motif peptide was 20 nM. The fitted value for the binding constant of the CPI-motif peptide to CP was 21.5 nM, which is within the range of experimental values determined from independent direct-binding experiments.