Monovalent Cation Requirement for the Aminoacyl Transfer Reaction in Protein Synthesis

Abstract

IN this laboratory, previous investigations of the transfer of amino-acids from aminoacyl sRNA to polypeptides on ribosomes (the aminoacyl transfer reaction) were carried out with cell fractions prepared from rat liver with buffered solutions containing potassium^1–3. The aminoacyl transfer reaction was dependent on the concentration of potassium ion in the incubation, and optimal incorporation was obtained when the concentration of potassium in the reaction mixture was between 0.075 and 0.1 M. Recent studies with preparations of Escherichia coli have shown that ammonium ions are more effective than potassium ions and that rubidium, caesium, sodium and lithium ions are much less active in promoting aminoacyl transfer^4,5. Because similar results have been obtained with the rat liver system, solutions containing ammonium are at present being routinely used in this laboratory⁶. This communication presents a detailed investigation of the effective concentrations of various monovalent cations on polypeptide biosynthesis. The results reveal an interesting relationship between the relative biological activity of these ions and some of their physical and chemical thermodynamic properties.