Figure 2.

TraR stability in E. coli in the presence and absence of AAI. Cells expressing TraR from a phage T7 promoter were treated with rifampicin to block host transcription, [³⁵S]methionine, and excess nonlabeled methionine 1 min later to inhibit radiolabeling. AAI was added to a final concentration of 1 μM 20 min (A), 2 min (B), 1 min (C), or 0 min (D) before the addition of the radiolabel, or 1 min (E) or 2 min (F) after the addition of label. In G, AAI was omitted. At various time intervals (0, 2, 4, 8, 16, and 64 min after the addition of nonlabeled methionine in lanes 1–6, respectively), aliquots were frozen at −80°C to terminate proteolysis, lysed, and cleared by ultracentrifugation. Radioactivities of soluble TraR were quantitated with the use of a Storm PhosphorImager. Calculated TraR half-lives are indicated at the right of each panel.