FIGURE 4.

Levels of CspA in extracts from cold-shock cells and stimulation of mRNA translation by purified CspA. The levels of CspA present in the S30 extracts from control and cold-shocked cells were determined as described (Brandi et al. 1999) by immunoblotting using polyclonal antibodies against CspA followed by densitometric quantification. The amounts of CspA normalized for the total amount of protein are expressed in (densitometric) arbitrary units and plotted as a function of the time of cold shock (A). The immunological quantification does not contain error bars, because in light of the excellent agreement of these data with the previously published results (La Teana et al. 1991; Brandi et al. 1999), this experiment was performed only once. In vitro translation of cspA mRNA (▴), hns mRNA (▾), P4hupB mRNA (♦), P3hupB mRNA (•), and P2hupB mRNA (▪) was carried out with 70S ribosomes and S100 supernatant from control cells in the presence of the indicated amounts of purified CspA. The other conditions are described in Materials and Methods, and the reaction mixtures were incubated for 30 min at 37°C (B) and for 90 min at 15°C (C). The results obtained are presented as the ratio of product synthesized in the presence of the indicated amounts of CspA versus the basal level product synthesized in the absence of CspA.