Experimental evidence for kinetic proofreading in the aminoacylation of tRNA by synthetase

The enzymatic aminoacylation of tRNA can be viewed as a means of proofreading either the amino acid or the tRNA or both. We have conducted further experimental tests of kinetic proofreading in discriminating between cognate and noncognate amino acids and tRNAs as follows: (formula: see text). In cases (i) and (ii) the amino acids are proofread, in cases (iii) and (iv) the tRNA is proofread, and in case (v), both the amino acid and the tRNA are proofread. ATP consumed per acylation was 400, 1.5, 40, 25, and 1000, respectively. High ATP/aminoacylation ratios are diagnostic for kinetic proofreading.