Mechanism for the definition of elongation and termination by the class II CCA-adding enzyme

Yukimatsu Toh, Daijiro Takeshita, Tomoyuki Numata, Shuya Fukai, Osamu Nureki, Kozo Tomita

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44 Citations (Scopus)


The CCA-adding enzyme synthesizes the CCA sequence at the 3′ end of tRNA without a nucleic acid template. The crystal structures of class II Thermotoga maritima CCA-adding enzyme and its complexes with CTP or ATP were determined. The structure-based replacement of both the catalytic heads and nucleobase-interacting neck domains of the phylogenetically closely related Aquifex aeolicus A-adding enzyme by the corresponding domains of the T. maritima CCA-adding enzyme allowed the A-adding enzyme to add CCA in vivo and in vitro. However, the replacement of only the catalytic head domain did not allow the A-adding enzyme to add CCA, and the enzyme exhibited (A, C)-adding activity. We identified the region in the neck domain that prevents (A, C)-adding activity and defines the number of nucleotide incorporations and the specificity for correct CCA addition. We also identified the region in the head domain that defines the terminal A addition after CC addition. The results collectively suggest that, in the class II CCA-adding enzyme, the head and neck domains collaboratively and dynamically define the number of nucleotide additions and the specificity of nucleotide selection.

Original languageEnglish
Pages (from-to)3353-3365
Number of pages13
JournalEMBO Journal
Issue number21
Publication statusPublished - Nov 2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Neuroscience
  • Molecular Biology
  • General Biochemistry,Genetics and Molecular Biology
  • General Immunology and Microbiology


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