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Crystal structures of Saccharomyces cerevisiae tryptophanyl-tRNA synthetase: new insights into the mechanism of tryptophan activation and implications for anti-fungal drug design.

ABSTRACT: Specific activation of amino acids by aminoacyl-tRNA synthetases is essential for maintaining translational fidelity. Here, we present crystal structures of Saccharomyces cerevisiae tryptophanyl-tRNA synthetase (sTrpRS) in apo form and in complexes with various ligands. In each complex, there is a sulfate ion bound at the active site which mimics the alpha- or beta-phosphate group of ATP during tryptophan activation. In particular, in one monomer of the sTrpRS-TrpNH(2)O complex, the sulfate ion appears to capture a snapshot of the alpha-phosphate of ATP during its movement towards tryptophan. Simulation study of a human TrpRS-Trp-ATP model shows that during the catalytic process the alpha-phosphate of ATP is driven to an intermediate position equivalent to that of the sulfate ion, then moves further and eventually fluctuates at around 2 A from the nucleophile. A conserved Arg may interact with the oxygen in the scissile bond at the transition state, indicating its critical role in the nucleophilic substitution. Taken together, eukaryotic TrpRSs may adopt an associative mechanism for tryptophan activation in contrast to a dissociative mechanism proposed for bacterial TrpRSs. In addition, structural analysis of the apo sTrpRS reveals a unique feature of fungal TrpRSs, which could be exploited in rational antifungal drug design.

SUBMITTER: Zhou M

PROVIDER: S-EPMC2879500 | biostudies-literature | 2010 Jun

REPOSITORIES: biostudies-literature

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Crystal structures of Saccharomyces cerevisiae tryptophanyl-tRNA synthetase: new insights into the mechanism of tryptophan activation and implications for anti-fungal drug design.

Zhou Minyun M Dong Xianchi X Shen Ning N Zhong Chen C Ding Jianping J

Nucleic acids research 20100131 10

Specific activation of amino acids by aminoacyl-tRNA synthetases is essential for maintaining translational fidelity. Here, we present crystal structures of Saccharomyces cerevisiae tryptophanyl-tRNA synthetase (sTrpRS) in apo form and in complexes with various ligands. In each complex, there is a sulfate ion bound at the active site which mimics the alpha- or beta-phosphate group of ATP during tryptophan activation. In particular, in one monomer of the sTrpRS-TrpNH(2)O complex, the sulfate ion ...[more]

PMID: 20123733

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Project description:Tryptophanyl-tRNA synthetase (TrpRS) is an essential enzyme that is recognizably conserved across all forms of life. It is responsible for activating and attaching tryptophan to a cognate tRNA(Trp) molecule for use in protein synthesis. In some eukaryotes this original core function has been supplemented or modified through the addition of extra domains or the expression of variant TrpRS isoforms. The three TrpRS structures from pathogenic protozoa described here represent three illustrations of this malleability in eukaryotes. The Cryptosporidium parvum genome contains a single TrpRS gene, which codes for an N-terminal domain of uncertain function in addition to the conserved core TrpRS domains. Sequence analysis indicates that this extra domain, conserved among several apicomplexans, is related to the editing domain of some AlaRS and ThrRS. The C. parvum enzyme remains fully active in charging tRNA(Trp) after truncation of this extra domain. The crystal structure of the active, truncated enzyme is presented here at 2.4Å resolution. The Trypanosoma brucei genome contains separate cytosolic and mitochondrial isoforms of TrpRS that have diverged in their respective tRNA recognition domains. The crystal structure of the T. brucei cytosolic isoform is presented here at 2.8Å resolution. The Entamoeba histolytica genome contains three sequences that appear to be TrpRS homologs. However one of these, whose structure is presented here at 3.0Å resolution, has lost the active site motifs characteristic of the Class I aminoacyl-tRNA synthetase catalytic domain while retaining the conserved features of a fully formed tRNA(Trp) recognition domain. The biological function of this variant E. histolytica TrpRS remains unknown, but, on the basis of a completely conserved tRNA recognition region and evidence for ATP but not tryptophan binding, it is tempting to speculate that it may perform an editing function. Together with a previously reported structure of an unusual TrpRS from Giardia, these protozoan structures broaden our perspective on the extent of structural variation found in eukaryotic TrpRS homologs.

Dataset Information

Crystal structures of Saccharomyces cerevisiae tryptophanyl-tRNA synthetase: new insights into the mechanism of tryptophan activation and implications for anti-fungal drug design.

Publications

Crystal structures of Saccharomyces cerevisiae tryptophanyl-tRNA synthetase: new insights into the mechanism of tryptophan activation and implications for anti-fungal drug design.

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