Two distinct regions in Staphylococcus aureus GatCAB guarantee accurate tRNA recognition |
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Authors: | Akiyoshi Nakamura Kelly Sheppard Junji Yamane Min Yao Dieter S?ll Isao Tanaka |
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Affiliation: | 1.Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan, 2.Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA, 3.Faculty of Advanced Life Science, Hokkaido University, kita-10, nishi-8, Sapporo, Hokkaido, 060-0810, Japan and 4.Department of Chemistry, Yale University, New Haven, CT 06520-8114, USA |
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Abstract: | In many prokaryotes the biosynthesis of the amide aminoacyl-tRNAs, Gln-tRNAGln and Asn-tRNAAsn, proceeds by an indirect route in which mischarged Glu-tRNAGln or Asp-tRNAAsn is amidated to the correct aminoacyl-tRNA catalyzed by a tRNA-dependent amidotransferase (AdT). Two types of AdTs exist: bacteria, archaea and organelles possess heterotrimeric GatCAB, while heterodimeric GatDE occurs exclusively in archaea. Bacterial GatCAB and GatDE recognize the first base pair of the acceptor stem and the D-loop of their tRNA substrates, while archaeal GatCAB recognizes the tertiary core of the tRNA, but not the first base pair. Here, we present the crystal structure of the full-length Staphylococcus aureus GatCAB. Its GatB tail domain possesses a conserved Lys rich motif that is situated close to the variable loop in a GatCAB:tRNAGln docking model. This motif is also conserved in the tail domain of archaeal GatCAB, suggesting this basic region may recognize the tRNA variable loop to discriminate Asp-tRNAAsn from Asp-tRNAAsp in archaea. Furthermore, we identified a 310 turn in GatB that permits the bacterial GatCAB to distinguish a U1–A72 base pair from a G1–C72 pair; the absence of this element in archaeal GatCAB enables the latter enzyme to recognize aminoacyl-tRNAs with G1–C72 base pairs. |
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