FIGURE 7.

Effect of individual initiation factors on the translation of cold-shock, cold-tolerant, and non-cold-shock mRNAs by 70S ribosomes at high and low temperature. Translation of cold-shock, cold-tolerant, and non-cold-shock mRNAs was performed under the conditions described in Materials and Methods with 70S ribosomes (20 pmoles) programmed with the indicated mRNAs (20 pmoles each) in the presence of S100 postribosomal fraction from control cells supplemented with 20 pmoles each of IF2 and IF3 (A,B), IF1 and IF3 (C,D), or IF1 and IF2 (E,F). In addition, each reaction mixture contained the amounts of IF1 (A,B), IF2 (B,C), or IF3 (D,E) indicated in the corresponding abscissa. Incubation was performed for 30 min at 37°C (A,C,E) or for 120 min at 15°C (B,D,F). For visualization of the translational stimulation produced by the increasing amounts of each factor, the results are presented as the ratio of the product obtained for each amount of IF1, IF2, and IF3 versus the basal level obtained in their absence. Cold-shock: cspAwt (▴), cspAΔ1-80 (▪), hns (•); cold-tolerant (gray symbols): P4hupB (♦), P3hupB (•), P2hupB (▪); non-cold-shock (white symbols): infA*AUU (○), infA*AUG (□), cspD (▵), hupA (▿). It should be noted that the translational stimulation displayed by each initiation factor is plotted using different scales in the ordinates.