tRNA-dependent amino acid discrimination by Escherichia coli valyl-tRNA synthetase

<p>Valyl-tRNA synthetase (ValRS) has difficulty discriminating between its cognate amino acid, valine, and structurally similar amino acids, particularly threonine. To minimize translational errors, the enzyme catalyzes a tRNA-dependent editing reaction that prevents accumulation of misacylated tRNA Val. Replacing the universally conserved 3' terminal A of tRNAVal, particularly with pyrimidines (C or U), permits stable misacylation with threonine, alanine, serine, and cysteine. We also observe low levels of aminoacylation of wild type and 3'-end mutants of tRNAVal with isoleucine. ValRS is unable to hydrolytically deacylate misacylated tRNAVal terminating in 3' pyrimidines, but can deacylate tRNAVal terminating in purines (G or A). Evidently, a purine at position 76 of tRNA is necessary for translational editing by ValRS. These misacylated mutant tRNAs act as noncompetitive inhibitors of the aminoacylation reaction. Numerous tRNA mutants have been used to investigate the nucleotides and structural features of tRNA essential for editing. A direct correlation was found between the aminoacylation efficiency of a tRNA and its ability to stimulate the editing reaction, suggesting that editing occurs at the posttransfer step. To identify functional groups on the 3' terminal nucleotide required for function, we replaced the conserved A76 with several different nucleoside analogs and measured their effect on the aminoacylation and editing activity of the tRNA.</p>

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

dissertation

Department dc:contributor.department

Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology (LAS)

Year dc:date.issued

2000

Author dc:creator

• Tardif, Keith

Advisor dc:contributor.advisor

• Jack Horowitz

Language dc:language.iso

en

DOI

https://doi.org/10.31274/rtd-180813-13561

Identifier

archive/lib.dr.iastate.edu/rtd/12289/

OAI identifier oai:identifier

oai:dr.lib.iastate.edu:20.500.12876/65640