Effect of temperature on translation of mRNA coding for an extracellular proteinase and cell proteins inBacillus megaterium

The content and the half-life of mRNA coding for the Ca²⁺-dependent metalloproteinase were measured by determining the enzyme activity excreted into the medium by cells pregrown in the absence of Ca²⁺ after addition of Ca²⁺ and actinomycin D. The content of the functional proteinase mRNA was highest at 31°C, which is the optimal temperature for the synthesis of this enzyme. Its half-life was 15 min, 7 min, and less than 2 min at 24°, 35°, and 42°C, respectively. Only the third of mRNA molecules synthesized at 31°C was translated in vivo into an active enzyme at 42°C, when compared with the translation proceeding at 24°C. Two-thirds of mRNA molecules synthesized at 31°C were translated into stable cell proteins at 42°C when compared with translation at 24°C. The mean half-life of mRNAs coding for cell proteins was 6–7 min at 24°C, 3 min at 35°C and 2 min at 42°C.