Fig. 7. The role of UmuD in removal of excess UmuD′ by ClpXP-mediated degradation. Purified UmuD/D′ was mixed with UmuD′ and incubated in the presence of ClpXP at 37°C for the indicated times. Aliquots were removed, processed and visualized as described in Materials and methods. In this experiment, UmuD′ was targeted for ClpXP-mediated proteolysis despite the fact that it is in a 3-fold molar excess over UmuD. Similar results were also obtained when UmuD′ was in 6-fold excess over UmuD (not shown).