Figure 6.

Heat-shock response. (A) Cells were grown in minimal media at 30°C and then shifted to 42°C. At the times indicated, samples were incubated with [³⁵S]methionine for 2 min. Samples were separated by 4%-12% PAGE. The positions of DnaK, GroE, and an 89-kD protein likely to be Lon are indicated. (^*) Major proteins whose expression decreases on heat shock; the top band is β′::σ⁷⁰, and the next-to-top band is β, β′. Relative GroE levels are averages of four experiments. (•) Wild-type (RL301); (○) β′::σ⁷⁰ strain with chromosomally encoded σ⁷⁰ (RL1374). (B) Immunoblot analysis using antibodies against σ³² (Materials and Methods). (Lanes 1-3) Wild-type whole-cell lysate (MC1060). (Lanes 4-6) β′::σ⁷⁰ whole-cell lysate (RL1454). (Lanes 7-9) His₆-tagged σ³². Equal amounts of total cellular protein were electrophoresed.