Human Tyrosyl-tRNA Synthetase Shares Amino Acid Sequence Homology with a Putative Cytokine

Theresa A Kleeman,Dongbing Wei,Keith L Simpson,Eric A First

doi:10.1074/jbc.272.22.14420

Theresa A Kleeman, Dongbing Wei + Show 2 more

Open Access

https://doi.org/10.1074/jbc.272.22.14420

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Abstract

To test the hypothesis that tRNATyr recognition differs between bacterial and human tyrosyl-tRNA synthetases, we sequenced several clones identified as human tyrosyl-tRNA synthetase cDNAs by the Human Genome Project. We found that human tyrosyl-tRNA synthetase is composed of three domains: 1) an amino-terminal Rossmann fold domain that is responsible for formation of the activated E.Tyr-AMP intermediate and is conserved among bacteria, archeae, and eukaryotes; 2) a tRNA anticodon recognition domain that has not been conserved between bacteria and eukaryotes; and 3) a carboxyl-terminal domain that is unique to the human tyrosyl-tRNA synthetase and whose primary structure is 49% identical to the putative human cytokine endothelial monocyte-activating protein II, 50% identical to the carboxyl-terminal domain of methionyl-tRNA synthetase from Caenorhabditis elegans, and 43% identical to the carboxyl-terminal domain of Arc1p from Saccharomyces cerevisiae. The first two domains of the human tyrosyl-tRNA synthetase are 52, 36, and 16% identical to tyrosyl-tRNA synthetases from S. cerevisiae, Methanococcus jannaschii, and Bacillus stearothermophilus, respectively. Nine of fifteen amino acids known to be involved in the formation of the tyrosyl-adenylate complex in B. stearothermophilus are conserved across all of the organisms, whereas amino acids involved in the recognition of tRNATyr are not conserved. Kinetic analyses of recombinant human and B. stearothermophilus tyrosyl-tRNA synthetases expressed in Escherichia coli indicate that human tyrosyl-tRNA synthetase aminoacylates human but not B. stearothermophilus tRNATyr, and vice versa, supporting the original hypothesis. It is proposed that like endothelial monocyte-activating protein II and the carboxyl-terminal domain of Arc1p, the carboxyl-terminal domain of human tyrosyl-tRNA synthetase evolved from gene duplication of the carboxyl-terminal domain of methionyl-tRNA synthetase and may direct tRNA to the active site of the enzyme.

Highlights

The nucleotide sequence(s) reported in this paper has been submitted to the GenBankTM/EBI Data Bank with accession number(s) U89436
If the hypothesis that tRNATyr recognition differs between bacterial and eukaryotic tyrosyl-tRNA synthetases is correct, one would predict that these differences should show up in three different ways
Differences in tRNATyr recognition should be reflected in the amino acid sequences of bacterial and eukaryotic tyrosyl-tRNA synthetases

Summary

Introduction

The nucleotide sequence(s) reported in this paper has been submitted to the GenBankTM/EBI Data Bank with accession number(s) U89436. None of the eleven amino acids known to be involved in tRNATyr recognition [42,43,44,45,46,47] are conserved between the human and B. stearothermophilus tyrosyl-tRNA synthetases, suggesting that in contrast to the mechanism for formation of the E1⁄7Tyr-AMP intermediate, tRNATyr recognition differs between eukaryotes, archaea, and bacteria.

Results

Conclusion