FIGURE 3.

Presence of a trans-acting factor in the postribosomal supernatant (S100) of cold-shocked cells. (A) Translation of cspA mRNA was carried out to completion at 15°C (gray) and 37°C (black) in the presence of E. coli MRE600 70S ribosomes supplemented with the indicated amounts of postribosomal supernatants (S100) derived from either control or cold-shocked cells. These S100 fractions were prepared as described in Materials and Methods and exhaustively dialyzed against Buffer A and adjusted to the same protein concentration just before use. Translation was carried out as described in Materials and Methods, and the values reported in the ordinate are the ratios of the levels of protein synthesized with S100 from cold-shocked (60 min at 10°C) versus control cells. (B) Translation of cspA mRNA was carried out at 15°C and 37°C in the presence of increasing amounts of S30 extract from control cells (black) and from cells carrying extra copies of cspA (gray) as described in Materials and Methods. The other conditions are as described above. The values reported in the ordinate are the ratios between the maximum levels of protein synthesized at saturation by each S30 extract at 15°C and 37°C. No error bars are given for this experiment, as the translational ratios were obtained by dividing single experimental points obtained in a single experiment. However, essentially identical results were obtained when a similar experiment was repeated under somewhat different experimental conditions.