Degree Type

Dissertation

Date of Award

2000

Degree Name

Doctor of Philosophy

Department

Biochemistry, Biophysics and Molecular Biology

First Advisor

Jack Horowitz

Abstract

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.

DOI

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

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Keith David Tardif

Language

en

Proquest ID

AAI9977365

File Format

application/pdf

File Size

131 pages

Included in

Biochemistry Commons

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