FIG. 4.
Coexpression of OmpT-PA with some of the compounds of the Sec machinery. (A) E. coli K5 host cells transformed with the indicated plasmids were grown in LB medium supplemented with chloramphenicol (25 μg/ml) at 28°C to an A600 of 0.6. IPTG (0.5 mM) was added, and incubation was continued for 6 h. The activity of PA in the control E. coli K5 culture transformed with pPAOT was taken as 1. Error bars indicate standard deviations. (B) Western blot of the periplasmic fraction of the same samples as those used for activity measurements in panel A. The protein concentration load per lane corresponds to the same amount of cells verified by optical density measurements. Pure PA (0.1 mg/ml) was used as a standard (PAst).