Elongation factor Tu can reduce translation errors in poly(U)-directed cell-free systems

Abstract

Rates of incorporation of [ 3H]phenylalanine and [ 14C]leucine from the aminoacylated transfer-RNA into polypeptides synthesized on poly(U) programmed Escherichia coli ribosomes have been determined in cell-free translation systems containing either elongation factors Tu and G with GTP, or just elongation factor Tu or G with GTP, or none of the elongation factors. The presence of elongation factor Tu with GTP has been shown to reduce the leucine to phenylalanine ratio in the product at relatively low concentrations of Mg 2+. This error-reducing effect of elongation factor Tu has not been observed at high concentrations of Mg 2+, although the factor still contributed to the speed of elongation. The results are discussed in terms of the kinetic proof-reading mechanism proposed by Hopfield (1974).