Protein Synthesis in a Cell-free System from an Extreme Thermophile

Effects of Preincubation in the Cold on Polyuridylic Acid-dependent Polyphenylalanine Synthesis at High Temperature

抄録

1. It was found that preincubation of the reaction mixture in the cold enhanced polyuridylic acid-directed polyphenylalanine synthesis by a cell-free extract of Thermus thermophilus HB8 at high temperature.
2. The effect of preincubation was most marked at 10-25° in the presence of 20mM Mg²⁺, Preincubation at 65° failed to stimulate the incorporation.
3. The presence of phenylalanyl-tRNA, polyuridylic acid, and ribosomes was essential for preincubation in the cold to be effective.
4. A ternary complex of amino acyl-tRNA, polyuridylic acid, and a ribosome formed at low temperature was isolated by CPG-10 column chromatography; the isolated complex initiated polyphenylalanine synthesis effectively at high temperature.
5. The amount of the ternary complex formed depends on the preincubation time and the concentration of Mg²⁺. Since the amount of the complex correlated positively to the rate of polyphenylalanine synthesis at high temperature, the effectiveness of preincubation in the cold is presumably due to the formation of the ternary complex of phenylalanyl-tRNA, polyuridylic acid, and a ribosome.