Figure 3.

In triplicate, a coumarin reporter (Suc-LLVY-AMC) of proteasome activity was used to determine the stimulating ability of 500 μM sodium dodecyl sulfate (SDS). For comparison, this was also performed using the FRET reporter. The basal level of activity determined by each reporter was normalized to 100%. Using the coumarin reporter, SDS stimulated the hydrolysis activity 2.4x, whereas FRET reporter hydrolysis was stimulated 8.3x. Therefore, the FRET reporter increases the dynamic range of measurable stimulated activity.