Figure 4.

Hsp90 speeds the recovery of heat-inactivated firefly luciferase. Firefly luciferase was inactivated at 42°C as described in the legend of Fig. 3. With the addition of a protein synthesis inhibitor, cells were returned to 34°C (a temperature at which most Hsp90 activity is lost in the hsp90^G170D mutant). The recovery of previously synthesized, heat-inactivated firefly luciferase was monitored in wild-type (□) and hsp90^G170D (⋄) cells as described in the text. Enzyme activities were normalized to the activity present in each strain prior to heat inactivation. Data are the means and standard deviations of three independent experiments using three independent transformants.