Measurement of Acceptor-T Psi C Helix Length of tRNA for Terminal A76-Addition by A-Adding Enzyme.Yamashita, S., Martinez, A., Tomita, K.
(2015) Structure 23: 830-842
- PubMed: 25914059
- DOI: https://doi.org/10.1016/j.str.2015.03.013
- Primary Citation of Related Structures:
4WBY, 4WBZ, 4WC0, 4WC1, 4WC2, 4WC3, 4WC4, 4WC5, 4WC6, 4WC7, 4X0A, 4X0B
- PubMed Abstract:
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-TΨC 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.
Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1, Higashi, Tsukuba, Ibaraki 305-8566, Japan.