Figure 1.

LexA auto-cleavage fragments are captured and degraded by ClpXP. (A) Western blot of the LexA species captured by the ClpP^trap and generated by auto-cleavage in vitro. (B) The proteolytic stability of LexA, LexA^1–84, and LexA^85–202 in vivo was determined in clpX⁺ (MC4100) and clpX⁻ (SG22101) strains bearing plasmid pJL42. LexA, LexA^1–84, and LexA^85–202 were identified by comparison with auto-cleaved LexA (lane S). It is difficult to see the continued disappearance of LexA, as expected from auto-processing, because the Western blots are mildly overexposed to allow observation of the low levels of LexA^85–202. (C) ClpXP degradation of purified LexA, LexA^1–84, and LexA^85–202 in vitro. The band marked ATP-RS is creatine kinase.