Protein Synthesis in a Cell-Free System Derived from Rabbit Liver 1

Summary

A cell-free amino acid incorporating system was prepared from rabbit liver tissue and shown to possess more activity than previously described mammalian cell-free systems. The active pH 5 enzyme fraction prepared from rabbit liver tissue was inhibited by added rabbit liver or rat liver transfer factors. The optimal conditions for endogenous amino acid incorporation revealed an optimal Mg²⁺ ion concentration of 10 mM with an extended time course of incorporation. The addition of poly U stimulated the incorporation of phenylalanine into protein by approximately 20-40-fold with an upward shift in optimal Mg²⁺ ion concentration. The incorporation of amino acids depended on the concentration of energy sources, amino acids, and an optimal pH and temperature of the incubation mixtures.