Figure 2.

Exposure to paraquat or cadmium stimulates the degradation of recently synthesized but not long-lived proteins, and 60 min after synthesis, proteins no longer show this response to paraquat and cadmium. (A) During exponential growth at 30°C, yeast were exposed to 80 μg/ml paraquat or 50 μg/ml cadmium for 90 min, and then ³⁵S-Met was added for 5 min at 30°C to label recently synthesized proteins or for 90 min to label long-lived proteins. After washing and resuspension in chase medium, rates of protein degradation were measured as in Fig. 1 A. (B) Proteins were labeled with ³⁵S-Met for 5 min, washed, and then paraquat and cadmium were added immediately or 60 min after synthesis. The amounts of degradation after 1 h were measured. Degradation rates after 2 and 3 h showed similar differences as after 1 h (not depicted).