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

作者：Toh Yukimatsu; Takeshita Daijiro; Numata Tomoyuki; Fukai Shuya; Nureki Osamu; Tomita Kozo^*

来源：The EMBO Journal, 2009, 28(21): 3353-3365.

DOI：10.1038/emboj.2009.260

• CCA
• nucleotidyltransferase
• template-independent
• tRNA

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. The EMBO Journal (2009) 28, 3353-3365. doi: 10.1038/emboj.2009.260; Published online 10 September 2009

• 出版日期2009-11-4
• 单位河北医科大学