Further observations on the polynucleotide-induced stimulation of protein synthesis by cell-free preparations from rabbit reticulocytes

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Abstract
The effect of high-molecular-weight ribonucleic acid (RNA) from reticulocyte polyribosomes (messenger RNA) on protein synthesis by subcellular fractions derived from reticulocytes, reported by Arnstein, Cox and Hunt (1964), has now been studied in detail. Optimum response of the cell-free system requires 30-50m[image] K+ and approx. 5 m[image] Mg2+ in the pH range 7.4-7.6. RNA stimulates the incorporation into protein of both free amino acids and of aminoacyl residues from s-RNA. Stimulation by either RNA or polyuridylic acid is dependent on a labile factor or enzyme, which is present in the "pH 5 fraction" and may be concerned with the formation of new polysomes. Quantitatively the response of the cell-free system to RNA is similar to that of polyuridylic acid, and there appears to be competition between messenger RNA and polyuridylic acid or polyadenylic acid.