The Effect of Magnesium‐Ion Concentration on the Translation of Phage‐f2 RNA in a Cell‐Free System of Escherichia coli

The phage‐f2 specific protein synthesis was studied in the cell‐free system of Escherichia coli at 10.6–18.6 mM Mg 2+ . The products formed under the direction of f2 RNA between 12.6 mM and 18.6 mM Mg 2+ were separated by polyacrylamide gel electrophoresis and found to correspond to phage‐specific proteins, i. e. RNA synthetase and the coat protein. The rate of f2‐RNA translation was optimal at 12.6 mM Mg 2+ . Lowering of Mg 2+ concentration from the optimal value to 10.6 mM caused the lack of formation of complete RNA synthetase while the coat protein was still synthesised. This was due to a sharp decrease in rate of polypeptide‐chain elongation, which led to incomplete translation of the longer gene. Our results indicate that, within the studied range of Mg 2+ concentration, specific initiation of f2‐RNA translation occurs even at 18.6 mM Mg 2+ .