FIG. 7.

Increased stability of a mislocalized IMP in Δlon ΔclpYQ cells. Strains HDB97 (lon⁺ clpYQ⁺) and HDB107 (Δlon ΔclpYQ) transformed with pTRC or pTRC-ftsY (G385A) were grown in LB containing ampicillin. IPTG (2 mM) was added to induce expression of the mutant ftsY allele and 0.2% arabinose (ara) was added 20 min later to induce expression of the AcrB 576-AP fusion protein. Samples were removed from each culture 10 min (lanes 1 to 4) and 20 min (lanes 5 to 8) after the addition of ara, and proteins were precipitated with 10% TCA. The steady-state level of the AP fusion protein was determined by Western blotting. Lanes 1, 2, 5, and 6, strain HDB97; lanes 3, 4, 7, and 8, strain HDB107. ftsY (G385A) was expressed in lanes 2, 4, 6, and 8. The amount of AcrB 576-AP detected after inhibition of the SRP pathway is expressed as a percentage of the fusion protein detected in control cells.