The ability of aminoacyl-tRNA synthetases to distinguish between similar amino acids is crucial for accurate translation of the genetic code. Saccharomyces cerevisiae seryl-tRNA synthetase (SerRS) employs tRNA-dependent recognition of its cognate amino acid serine [Lenhard, B., Filipic, S., Landeka, I., Skrtic, I., Söll, D. & Weygand-Durasevic, I. (1997) J. Biol. Chem.272, 1136-1141]. Here we show that dimeric SerRS enzyme complexed with one molecule of tRNASer is more specific and more efficient in catalyzing seryl-adenylate formation than the apoenzyme alone. Sequence-specific tRNA-protein interactions enhance discrimination of the amino acid substrate by yeast SerRS and diminish the misactivation of the structurally similar noncognate threonine. This may proceed via a tRNA-induced conformational change in the enzyme's active site. The 3'-terminal adenosine of tRNASer is not important in effecting the rearrangement of the serine binding site. Our results do not provide an indication for a readjustment of ATP binding in a tRNA-assisted manner. The stoichiometric analyses of the complexes between the enzyme and tRNASer revealed that two cognate tRNA molecules can be bound to dimeric SerRS, however, with very different affinities.

• PMID: 12392560
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Journal Article | Research Support, Non-U.S. Gov't | Research Support, U.S. Gov't, P.H.S.

Authors

Gruic-Sovulj I, Landeka I, Söll D, Weygand-Durasevic I

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