FIG. 3.

Effect of 0.5 mM spermidine on protein synthesis (A) and on the levels of ribosomal particles (B) in the speG mutant. Strain CAG2242 was grown in LB medium to mid-log phase and shifted to 7°C. (A) Following the shift to 7°C, strain CAG2242 in the absence and presence of spermidine was pulse-labeled with [³⁵S]methionine (1, 48, and 72 h postshift) and radioactivity in the trichloroacetic acid-insoluble material was counted as described in Materials and Methods. The counts were normalized to the amount of protein present. The values were normalized to the value obtained at 1 h. Time zero represents the time of the shift to 7°C and/or the addition of 0.5 mM spermidine. (B) Sedimentation profiles of extracts of strain CAG2242 in the absence and presence of 0.5 mM spermidine were prepared as described in Materials and Methods. Extracts were prepared from cells growing for 72 h at 7°C.