Figure S2 - FRET-based clamp binding and release assays for delta’-E mutants. Steady-state fluorescence emission spectra obtained with excitation at 460 nm. Samples contained 500 nM fluorescein-labeled D106C delta-A in clamp loader + 4 uM D253C beta labeled with TMR. Relative clamp binding and release calculated from these data is shown in Figure 4.