Figure 7. Ligand binding assays: Retinol binding to altered IRBP proteins.

One micromolar protein was used in each sample. The concentrations of the ligand are shown on the abscissa, and the fluorescence difference between the sample (protein plus retinol) and the blank (retinol only) in photons counted per second (cps) is shown on the ordinate. The raw data from all-trans-retinol titrations of the WT insect cell-derived protein and from the E. coli produced individual repeats proteins are shown. The results from four independent assays are averaged. The error bars indicate the standard error of the mean. WT protein (in black) shows the highest binding followed by EcR1 in red, EcR2 in green, EcR3 in blue, and EcR4 in violet.