Two Complementary Enzymes for Threonylation of tRNA in Crenarchaeota: Crystal Structure of Aeropyrum pernix Threonyl-tRNA Synthetase Lacking a cis-Editing Domain |
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Authors: | Satoru Shimizu Yoshiteru Sato Yu-ichiro Miyashita Kaoru Suzuki Masaru Tsunoda Anne-Catherine Dock-Bregeon Akio Takénaka |
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Institution: | 1 Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuda, Midori-ku, Yokohama 226-8501, Japan 2 College of Science and Engineering, Iwaki-Meisei University, Chuodai-iino, Iwaki, Fukushima 970-8551, Japan 3 Faculty of Pharmacy, Iwaki-Meisei University, Chuodai-iino, Iwaki, Fukushima 970-8551, Japan 4 Departement de Biologie et Génomique Structurales, Institut de Génétique et de Biologie Moléculaire et Cellulaire, 1, Rue Laurent Fries, F-67404 Illkirch, France |
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Abstract: | In protein synthesis, threonyl-tRNA synthetase (ThrRS) must recognize threonine (Thr) from the 20 kinds of amino acids and the cognate tRNAThr from different tRNAs in order to generate Thr-tRNAThr. In general, an organism possesses one kind of gene corresponding to ThrRS. However, it has been recently found that some organisms have two different genes for ThrRS in the genome, suggesting that their proteins ThrRS-1 and ThrRS-2 function separately and complement each other in the threonylation of tRNAThr, one for catalysis and the other for trans-editing of misacylated Ser-tRNAThr. In order to clarify their three-dimensional structures, we performed X-ray analyses of two putatively assigned ThrRSs from Aeropyrum pernix (ApThrRS-1 and ApThrRS-2). These proteins were overexpressed in Escherichia coli, purified, and crystallized. The crystal structure of ApThrRS-1 has been successfully determined at 2.3 Å resolution. ApThrRS-1 is a dimeric enzyme composed of two identical subunits, each containing two domains for the catalytic reaction and for anticodon binding. The essential editing domain is completely missing as expected. These structural features reveal that ThrRS-1 catalyzes only the aminoacylation of the cognate tRNA, suggesting the necessity of the second enzyme ThrRS-2 for trans-editing. Since the N-terminal sequence of ApThrRS-2 is similar to the sequence of the editing domain of ThrRS from Pyrococcus abyssi, ApThrRS-2 has been expected to catalyze deaminoacylation of a misacylated serine moiety at the CCA terminus. |
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Keywords: | Ap ThrRS ThrRSs from Aeropyrum pernix StThrRS ThrRSs from Sulfolobus tokodaii EcThrRS ThrRSs from Escherichia coli SaThrRS ThrRSs from Staphylococcus aureus PaThrRS ThrRSs from Pyrococcus abyssi ARS aminoacyl-tRNA synthetase Thr-AMS 5&prime l-threonyl)-sulfamoyl)adenosine" target="_blank">-O-(N-(l-threonyl)-sulfamoyl)adenosine ThrRS threonyl-tRNA synthetase tRNAA tRNA corresponding to the cognate amino acid MAD multiple anomalous dispersion PDB Protein Data Bank |
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