Figure 3.

Effects of varying length of pulse labeling on σ³² synthesis on heat shock. (A and C) SDS/PAGE patterns of σ³² synthesized in MC4100 or MG1655. Cells were grown in minimal medium at 30°C, shifted to 42°C, and samples taken at various points were pulse labeled for the indicated period with [³⁵S]Met (600 Ci/mmol, 100 μCi/ml for 60-s pulse; 1,200 Ci/mmol, 100 μCi/ml for 30- or 15-s pulse). (◃) The labeled σ³² was precipitated and analyzed by SDS/PAGE as in Fig. 2A. (◂) Reference protein to correct for sample loss. (B and D) Quantitation of relative synthesis rates. The band intensities were quantified and normalized to the maximum value (set as 100) for each experiment and shown as relative synthesis rates. Average values of at least three independent experiments are presented with standard errors.