FIGURE 1.

CpxPΔ151 CpxP has two functions. A, steady-state analysis of PapE by immunological determination according to an established protocol (11) with two modifications as described in detail under “Experimental Procedures.” Cells expressing PapE-Strep and indicated CpxP variants were subjected to immunological determination using antiserum to the Strep-tag, the CpxP protein, and the MalE protein (loading control), respectively. B, CpxA autophosphorylation activity was measured by incubating proteoliposomes containing purified CpxA-His6 (1 μm) in phosphorylation buffer containing [γ-³²P]ATP for 20 min. To test the influence of CpxP variants on CpxA autophosphorylation, the experiment was performed as described (12) with wild-type CpxP or CpxPΔ151-loaded proteoliposomes. Samples were separated by SDS-PAGE and, analyzed as phosphorimages, and the amounts of [³²P]ATP were quantified by phospho imaging using [γ-³²P]ATP as a standard. Shown are averages ± S.E. from three different experiments (t test).