TAILIEUCHUNG - Báo cáo Y học: tRNA-dependent amino acid discrimination by yeast seryl-tRNA synthetase

The ability of aminoacyl-tRNA synthetases to distinguish betweensimilaraminoacidsiscrucial foraccuratetrans-lation 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., So¨ll, D. & Weygand-Durasevic, I. (1997)J. Biol. , 1136–1141]. Herewe show that dimeric SerRS enzyme complexed with one molecule of tRNA Ser is more specific and more efficient in catalyzing seryl-adenylate formation than the apoenzyme alone. . | Eur. J. Biochem. 269 5271-5279 2002 FEBS 2002 doi tRNA-dependent amino acid discrimination by yeast seryl-tRNA synthetase Ita Gruic-Sovulj1 2 Irena Landeka1 2 Dieter Soil3 and Ivana Weygand-Durasevic1 2 1 Department of Chemistry Faculty of Science University of Zagreb Croatia 2Rudjer Boskovic Institute Zagreb Croatia 3Department of Molecular Biophysics and Biochemistry Yale University New Haven Connecticut USA 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. Still 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. Keywords tRNASer-SerRS complexes tRNA-dependent amino acid recognition amino acid selection tRNA binding covalent cross-linking. Accurate translation of genetic information is dependent on the high fidelity of several molecular processes. Different quality control mechanisms are adapted to prevent or correct naturally

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