title: Two complementary enzymes for threonylation of tRNA in crenarchaeota: crystal structure of Aeropyrum pernix threonyl-tRNA synthetase lacking a cis-editing domain.
abstract: In protein synthesis, threonyl-tRNA synthetase (ThrRS) must recognize threonine (Thr) from the 20 kinds of amino acids and the cognate tRNA(Thr) from different tRNAs in order to generate Thr-tRNA(Thr). 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 tRNA(Thr), one for catalysis and the other for trans-editing of misacylated Ser-tRNA(Thr). 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 A 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.
authors.affiliation: Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuda, Midori-ku, Yokohama 226-8501, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Shimizu
authors.forename: Ella Czarina Magat
authors.initials: EC
authors.lastname: Juan
authors.forename: Yoshiteru
authors.initials: Y
authors.lastname: Sato
authors.forename: Yu-Ichiro
authors.initials: Y
authors.lastname: Miyashita
authors.forename: Md Mominul
authors.initials: MM
authors.lastname: Hoque
authors.forename: Kaoru
authors.initials: K
authors.lastname: Suzuki
authors.forename: Tsubasa
authors.initials: T
authors.lastname: Sagara
authors.forename: Masaru
authors.initials: M
authors.lastname: Tsunoda
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sekiguchi
authors.forename: Anne-Catherine
authors.initials: AC
authors.lastname: Dock-Bregeon
authors.forename: Dino
authors.initials: D
authors.lastname: Moras
authors.forename: Akio
authors.initials: A
authors.lastname: Takénaka
mesh_terms: D041522:Aeropyrum / Q000201:enzymology / Q000378:metabolism*; D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D008969:Molecular Sequence Data; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D019642:RNA, Archaeal / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D013912:Threonine / Q000378:metabolism; D013914:Threonine-tRNA Ligase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D046249:Transfer RNA Aminoacylation
chemical_list: D019642:RNA, Archaeal; D012346:RNA, Transfer, Amino Acyl; D013912:Threonine; D013914:Threonine-tRNA Ligase