Figure 4.

Cyclic IXP1 inhibits degradation of λ O by ClpXP. λ O protein was incubated with ClpXP in the presence or absence of IXP1, and the loss of intact substrate was monitored by SDS-PAGE. Representative SDS-polyacrylamide gels stained with Coomassie blue showing the amount of λ O protein at various times after addition of ClpXP are shown. The amount of λ O protein remaining was plotted versus time and fit with a single exponential function to determine the substrate half-life. The average half-life for degradation of λ O was 35 ± 2 min in the absence of IXP1, and 73 ± 8 min in the presence of 100 μM IXP1.