Measurement of Acceptor-T Psi C Helix Length of tRNA for Terminal A76-Addition by A-Adding Enzyme

作者：Yamashita Seisuke; Martinez Anna; Tomita Kozo^*

来源：Structure, 2015, 23(5): 830-842.

DOI：10.1016/j.str.2015.03.013

The 3'-terminal CCA (C74C75A76-3') of tRNA is required for protein synthesis. In Aquifex aeolicus, the CCA-3' is synthesized by CC-adding and A-adding enzymes, although in most organisms, CCA is synthesized by a single CCA-adding enzyme. The mechanisms by which the A-adding enzyme adds only A76, but not C74C75, onto tRNA remained elusive. The complex structures of the enzyme with various tRNAs revealed the presence of a single tRNA binding site on the enzyme, with the enzyme measuring the acceptor-T Psi C helix length of tRNA. The 3'-C75 of tRNA lacking A76 can reach the active site and the size and shape of the nucleotide binding pocket at the insertion stage are suitable for ATP. The 3'-C74 of tRNA lacking C75A76 cannot reach the active site, although CTP or ATP can bind the active pocket. Thus, the A-adding enzyme adds only A76, but not C74C75, onto tRNA.

• 出版日期2015-5-5