Effect of Alcohols on Polypeptide Chain Elongation and Aminoacyl-tRNA Formation

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The effect of alcohols (methanol, ethanol, and propanol) on polypeptide chain elongation was studied. In the E. coli and rat liver cell-free systems, the optimal concentration of Mg²⁺ decreased with increase of ethanol concentration, although the maximum polyphenylalaniiie synthesis decreased. Methanol had almost the same effect as ethanol. Propanol decreased the optimal magnesium concentration, but polyphenylalanine synthetic activity was markedly decreased. The shift of optimal Mg²⁺ concentration by ethanol was also observed in polylysine and polysome-dependent polypeptide syntheses. Even in the presence of spermidine, ethanol caused the shift of optimal Mg²⁺ concentration. Ribosome-bound Mg²⁺ was decreased by the addition of ethanol.
A study of the effect of alcohols on aminoacyl-tRNA formation with ten amino acids in the absence of added Mg²⁺ showed that the formation of arginyl-, leucyl-, and valyl-tRNA was stimulated by the alcohols. Valyl-tRNA formation in the presence of alcohols was completely inhibited by EDTA, while that in the presence of Mg²⁺ was inhibited slightly by EDTA. No PP_i-ATP exchange was observed when alcohol was used as the only stimulant of valyl-tRNA formation.