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Publication Abstract from PubMed

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-TPsiC 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.

Measurement of Acceptor-TPsiC Helix Length of tRNA for Terminal A76-Addition by A-Adding Enzyme.,Yamashita S, Martinez A, Tomita K Structure. 2015 May 5;23(5):830-42. doi: 10.1016/j.str.2015.03.013. Epub 2015 Apr, 23. PMID:25914059^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.