FIG. 3.

Levels of ParE and ParC in synchronous cell cultures. (A) The 80-kDa ParE protein was detected by Western analysis of samples from a synchronous culture of strain CB15F at the times indicated. The last three lanes contain lysates of wild-type strain CB15, strain PC8830[divC307(Ts)], and strain PC4885[divC307(Ts), sueA020(Cs)], a spontaneous revertant of the divC307(Ts) strain grown at the restrictive temperature of 37°C. The level of the ParE protein was reduced in the divC307(Ts) strain and increased in the sueA020(Cs) strain relative to wild-type levels. Levels of ParE and ParC were quantified as described in Materials and Methods, and the level in swarmer cells at 0 min was normalized to 1.0 U. These measurements showed that the level of ParE increased from 1.0 U at 0 min to 2.1 U immediately before cell division at 0.8 to 0.9 division unit and then decreased after cell division to 1.6 U at 1.2 division units. Similar results were obtained when ¹²⁵I-labeled secondary antibodies were used; ParE levels determined in this assay (see Materials and Methods) increased from 1.0 U at 0 min to 1.9 U before division at 0.8 to 0.9 division unit and then decreased to 1.3 U after division at 1.2 division units. (B) The 87-kDa ParC protein was detected by Western analysis of lysates from a synchronous cell culture of strain CB15F. Assays of lysates of wild-type strains CB15 and PC8861[divF310(Ts)] grown at the restrictive temperature of 37°C are shown in the last two lanes. The level of the ParC protein was diminished in strain PC8861. Bands were quantified as described in Materials and Methods, but reproducible changes in ParC levels during the cell cycle were not detected.