Measurement of Acceptor-TΨC Helix Length of tRNA for Terminal A76-Addition by A-Adding Enzyme

Structure. 2015 May 5;23(5):830-842. doi: 10.1016/j.str.2015.03.013. Epub 2015 Apr 23.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Bacteria / chemistry
  • Bacteria / enzymology*
  • Bacteria / genetics
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Catalytic Domain
  • Crystallography, X-Ray
  • Cytidine Triphosphate / metabolism
  • Models, Molecular
  • Nucleic Acid Conformation
  • Protein Structure, Secondary
  • RNA Nucleotidyltransferases / chemistry*
  • RNA Nucleotidyltransferases / genetics
  • RNA Nucleotidyltransferases / metabolism*
  • RNA, Transfer / chemistry*
  • RNA, Transfer / metabolism
  • Substrate Specificity


  • Bacterial Proteins
  • Cytidine Triphosphate
  • Adenosine Triphosphate
  • RNA, Transfer
  • A adding enzyme
  • RNA Nucleotidyltransferases

Associated data

  • PDB/4WBY
  • PDB/4WBZ
  • PDB/4WC0
  • PDB/4WC1
  • PDB/4WC2
  • PDB/4WC3
  • PDB/4WC4
  • PDB/4WC5
  • PDB/4WC6
  • PDB/4WC7
  • PDB/4X0A
  • PDB/4X0B