1iq0
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THERMUS THERMOPHILUS ARGINYL-TRNA SYNTHETASE
OverviewOverview
Arginyl-tRNA synthetase (ArgRS) recognizes two major identity elements of, tRNA(Arg): A20, located at the outside corner of the L-shaped tRNA, and, C35, the second letter of the anticodon. Only a few exceptional organisms, such as the yeast Saccharomyces cerevisiae, lack A20 in tRNA(Arg). In the, present study, we solved the crystal structure of a typical, A20-recognizing ArgRS from Thermus thermophilus at 2.3 A resolution. The, structure of the T. thermophilus ArgRS was found to be similar to that of, the previously reported S. cerevisiae ArgRS, except for short insertions, and a concomitant conformational change in the N-terminal domain. The, structure of the yeast ArgRS.tRNA(Arg) complex suggested that two residues, in the unique N-terminal domain, Tyr(77) and Asn(79), which are, phylogenetically invariant in the ArgRSs from all organisms with A20 in, tRNA(Arg)s, are involved in A20 recognition. However, in a docking model, constructed based on the yeast ArgRS.tRNA(Arg) and T. thermophilus ArgRS, structures, Tyr(77) and Asn(79) are not close enough to make direct, contact with A20, because of the conformational change in the N-terminal, domain. Nevertheless, the replacement of Tyr(77) or Asn(79) by Ala, severely reduced the arginylation efficiency. Therefore, some, conformational change around A20 is necessary for the recognition., Surprisingly, the N79D mutant equally recognized A20 and G20, with only a, slight reduction in the arginylation efficiency as compared with the, wild-type enzyme. Other mutants of Asn(79) also exhibited broader, specificity for the nucleotide at position 20 of tRNA(Arg). We propose a, model of A20 recognition by the ArgRS that is consistent with the present, results of the mutational analyses.
About this StructureAbout this Structure
1IQ0 is a Single protein structure of sequence from Thermus thermophilus. Active as Arginine--tRNA ligase, with EC number 6.1.1.19 Full crystallographic information is available from OCA.
ReferenceReference
Structural and mutational studies of the recognition of the arginine tRNA-specific major identity element, A20, by arginyl-tRNA synthetase., Shimada A, Nureki O, Goto M, Takahashi S, Yokoyama S, Proc Natl Acad Sci U S A. 2001 Nov 20;98(24):13537-42. Epub 2001 Nov 6. PMID:11698642
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