FIG. 6.

Pulse-chase analysis of HemA[WT] and HemA[KK] expressed from F′ plasmids in S. typhimurium. (A) Top, TE7620 hemA60 recA/F′ hemA[WT]; bottom, TE7622 hemA60 recA/F′ hemA[KK]. The positions of HemA[WT] and HemA[KK] proteins are indicated. Cultures were grown and analyzed as described in the legend to Fig. 5, except that the chase was extended as shown above each lane. (B) An identical gel (not treated with fluor) was analyzed by using a PhosphorImager and ImageQuant software to calculate the half-life of the HemA protein. The HemA[WT] protein seen in TE7620 has a half-life of ca. 20 min, the same as that of the chromosomally encoded HemA protein (37). In contrast, the HemA[KK] protein seen in strain TE7622 is stable (half-life, >300 min).