title: Mechanism of 3'-Matured tRNA Discrimination from 3'-Immature tRNA by Class-II CCA-Adding Enzyme.
abstract: CCA-adding enzyme adds the 3'-CCA of tRNA, using CTP and ATP as substrates, and terminates RNA synthesis after completion of CCA addition, without using a nucleic acid template. The complex structure of class-II Thermotoga maritima CCA-adding enzyme and mature tRNA with 3'-CCA revealed the mechanisms by which the enzyme terminates RNA synthesis after completion of 3'-CCA addition, and discriminates 3'-mature tRNA from 3'-immature tRNA. After completion of 3'-CCA addition at the catalytic site, the 3'-CCA refolds and relocates to the release site, which is discrete from the catalytic site. The 3'-CCA forms a continuously stacked, stable conformation together with the enzyme. Consequently, the 3'-mature tRNA rotates relative to the surface of the enzyme, and only the 3'-mature tRNA is ready for release. The 3'-regions of immature tRNAs cannot form the stable stacking conformation in the release site; thus, the 3' end is relocated in the catalytic site, and the 3'-CCA is reconstructed.
authors.affiliation: Department of Computational Biology and Medical Sciences, Graduate School of Frontier Science, The University of Tokyo, Kashiwa, Chiba 277-8562, Japan; Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8566, Japan.
authors.forename: Seisuke
authors.initials: S
authors.lastname: Yamashita
authors.affiliation: Department of Computational Biology and Medical Sciences, Graduate School of Frontier Science, The University of Tokyo, Kashiwa, Chiba 277-8562, Japan; Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8566, Japan. Electronic address: kozo_tomita@cbms.k.u-tokyo.ac.jp.
authors.forename: Kozo
authors.initials: K
authors.lastname: Tomita
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D012316:RNA Nucleotidyltransferases / Q000737:chemistry* / Q000378:metabolism*; D012343:RNA, Transfer / Q000737:chemistry* / Q000378:metabolism*; D013379:Substrate Specificity; D020124:Thermotoga maritima / Q000737:chemistry / Q000201:enzymology / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D012343:RNA, Transfer; D012316:RNA Nucleotidyltransferases; C023198:tRNA nucleotidyltransferase