The integrity of the G2421-C2395 base pair in the ribosomal E-site is crucial for protein synthesis

RNA Biol. 2015;12(1):70-81. doi: 10.1080/15476286.2015.1017218.


During the elongation cycle of protein biosynthesis, tRNAs traverse through the ribosome by consecutive binding to the 3 ribosomal binding sites (A-, P-, and E- sites). While the ribosomal A- and P-sites have been functionally well characterized in the past, the contribution of the E-site to protein biosynthesis is still poorly understood in molecular terms. Previous studies suggested an important functional interaction of the terminal residue A76 of E-tRNA with the nucleobase of the universally conserved 23S rRNA residue C2394. Using an atomic mutagenesis approach to introduce non-natural nucleoside analogs into the 23S rRNA, we could show that removal of the nucleobase or the ribose 2'-OH at C2394 had no effect on protein synthesis. On the other hand, our data disclose the importance of the highly conserved E-site base pair G2421-C2395 for effective translation. Ribosomes with a disrupted G2421-C2395 base pair are defective in tRNA binding to the E-site. This results in an impaired translation of genuine mRNAs, while homo-polymeric templates are not affected. Cumulatively our data emphasize the importance of E-site tRNA occupancy and in particular the intactness of the 23S rRNA base pair G2421-C2395 for productive protein biosynthesis.

Keywords: 23S rRNA; E-site; E-tRNA; atomic mutagenesis; ribosome; translation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Pairing
  • Mutagenesis
  • Protein Biosynthesis*
  • RNA, Messenger / metabolism*
  • RNA, Transfer / metabolism*
  • Ribosomes / metabolism*
  • Thermus / chemistry*
  • Thermus / cytology*


  • RNA, Messenger
  • RNA, Transfer