1wyd

From Proteopedia

Revision as of 03:37, 21 November 2007

Crystal Structure of Aspartyl-tRNA synthetase from Sulfolobus tokodaii

Overview

In protein synthesis, 20 types of aminoacyl-tRNA synthetase (aaRS) are, generally required in order to distinguish between the 20 types of amino, acid so that each achieves strict recognition of the cognate amino acid, and the cognate tRNA. In the crenarchaeon Sulfolobus tokodaii strain 7, (St), however, asparaginyl-tRNA synthetase (AsnRS) is missing. It is, believed that AspRS instead produces Asp-tRNA(Asn) in addition to, Asp-tRNA(Asp). In order to reveal the recognition mechanism for the two, anticodons, GUC for aspartate and GUU for asparagine, the crystal, structure of St-AspRS (nondiscriminating type) has been determined at 2.3, A resolution as the first example of the nondiscriminating type of AspRS, from crenarchaea. A structural comparison with structures of, discriminating AspRSs indicates that the structures are similar to each, other overall and that the catalytic domain is highly conserved as, expected. In the N-terminal domain, however, the binding site for the, third anticodon nucleotide is modified to accept two pyrimidine bases, C, and U, but not purine bases. The C base can bind to form a hydrogen bond, to the surrounding main-chain amide group in the discriminating AspRS, while in the nondiscriminating AspRS the corresponding amino-acid residue, is replaced by proline, which has no amide H atom for hydrogen-bond, formation, thus allowing the U base to be accommodated in this site. In, addition, the residues that cover the base plane are missing in the, nondiscriminating AspRS. These amino-acid changes make it possible for, both C and U to be accepted by the nondiscriminating AspRS. It is, speculated that this type of nondiscriminating AspRS has been introduced, into Thermus thermophilus through horizontal gene transfer.

About this Structure

1WYD is a Single protein structure of sequence from Sulfolobus tokodaii with CL, SO4 and EPE as ligands. Full crystallographic information is available from OCA.

Reference

Structure of the nondiscriminating aspartyl-tRNA synthetase from the crenarchaeon Sulfolobus tokodaii strain 7 reveals the recognition mechanism for two different tRNA anticodons., Sato Y, Maeda Y, Shimizu S, Hossain MT, Ubukata S, Suzuki K, Sekiguchi T, Takenaka A, Acta Crystallogr D Biol Crystallogr. 2007 Oct;63(Pt 10):1042-7. Epub 2007, Sep 19. PMID:17881821

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