Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

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Igloi, G.L. et al.

Hydrolytic action of aminoacyl-tRNA synthetases from baker's yeast. "Chemical proofreading" of Thr-tRNA Val by valyl-tRNA synthetase studied with modified tRNA Val and amino acid analogues.

The properties of native and of two modified tRNA Val species in the correction of misactivated threonine by valyl-tRNA synthetase have been studied. Whereas Thr-tRNA Val-C-C-A could not be isolated in the valyl-tRNA synthetase catalyzed reaction, Thr-tRNA Val-C-C-3'dA is isolable in up to 50% yield in this system and tRNA Val-C-C-3'NH2A is fully aminoacylated with threonine by the same enzyme. The hydrolysis of preformed Thr-tRNA Val-C-C-A by free valyl-tRNA synthetase is 30 times faster than the corresponding breakdown of Val-tRNA Val-C-C-A. This hydrolytic activity is also observed with Thr-tRNA Val-C-C-3'dA although the rate is reduce to that of the reaction of Val-tRNA Val-C-C-A. Modification of the threonine to O-methylthreonine, which is also a substrate for valyl-tRNA synthetase, leads to stabilization of the O-methylthreonyl-tRNA esters. The AMP/PP independent hydrolysis under aminoacylating conditions, which is a measure of the correction process, indicates that O-MeThr-tRNA Val-C-C-A is only very slowly corrected while the tRNA Val-C-C-3'dA and tRNA Val-C-C-3'NH2A esters are completely stable. Removal of the methoxy group of O-methylthreonine as in alpha-amino-butyric acid increases the rate of the hydrolytic reaction and once again alpha-Abu-tRNA Val-C-C-A and alpha-Abu-tRNA Val-C-C-3'dA are unstable under aminoacylating conditions and not isolable.[1]

References

Hydrolytic action of aminoacyl-tRNA synthetases from baker's yeast. "Chemical proofreading" of Thr-tRNA Val by valyl-tRNA synthetase studied with modified tRNA Val and amino acid analogues. Igloi, G.L., von der Haar, F., Cramer, F. Biochemistry (1977) [Pubmed]

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