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Structure. 2016 Jun 7;24(6):918-25. doi: 10.1016/j.str.2016.03.022. Epub 2016 Apr 28.

Mechanism of 3'-Matured tRNA Discrimination from 3'-Immature tRNA by Class-II CCA-Adding Enzyme.

Author information

1
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.
2
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.

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.

PMID:
27133023
DOI:
10.1016/j.str.2016.03.022
[Indexed for MEDLINE]
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