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. 1990 Jun;87(12):4504–4508. doi: 10.1073/pnas.87.12.4504

Proofreading in vivo: editing of homocysteine by methionyl-tRNA synthetase in Escherichia coli.

H Jakubowski 1
PMCID: PMC54144  PMID: 2191291

Abstract

Previous in vitro studies have established a pre-transfer proofreading mechanism for editing of homocysteine by bacterial methionyl-, isoleucyl-, and valyl-tRNA synthetases. The unusual feature of the editing is the formation of a distinct compound, homocysteine thiolactone. Now, two-dimensional TLC analysis of 35S-labeled amino acids extracted from cultures of the bacterium Escherichia coli reveals that the thiolactone is also synthesized in vivo. In E. coli, the thiolactone is made from homocysteine in a reaction catalyzed by methionyl-tRNA synthetase. One molecule of homocysteine is edited as thiolactone per 109 molecules of methionine incorporated into protein in vivo. These results not only directly demonstrate that the adenylate proofreading pathway for rejection of misactivated homocysteine operates in vivo in E. coli but, in general, establish the importance of error-editing mechanisms in living cells.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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