Study of the functional interaction of the 900 tetraloop of 16 S ribosomal RNA with helix 24 within the bacterial ribosome

François Bélanger, Matthieu G. Gagnon, Sergey V. Steinberg, Philip R. Cunningham, Léa Brakier-Gingras

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


The 900 tetraloop that caps helix 27 of 16S ribosomal RNA (rRNA) is amongst the most conserved regions of rRNA. This tetraloop forms a GNRA motif that docks into the minor groove of three base-pairs at the bottom of helix 24 of 16S rRNA in the 30S subunit. Both the tetraloop and its receptor in helix 24 contact the 23S rRNA, forming the intersubunit bridge B2c. Here, we investigated the interaction between the 900 tetraloop and its receptor by genetic complementation. We used a specialized ribosome system in combination with an in vivo instant evolution approach to select mutations in helix 24 compensating for a mutation in the 900 tetraloop (A900G) that severely decreases ribosomal activity, impairing subunit association and translational fidelity. We selected two mutants where the G769-C810 base-pair of helix 24 was substituted with either U-A or C·A. When these mutations in helix 24 were investigated in the context of a wild-type 900 tetraloop, the C·A but not the U-A mutation severely impaired ribosome activity, interfering with subunit association and decreasing translational fidelity. In the presence of the A900G mutation, both mutations in helix 24 increased the ribosome activity to the same extent. Subunit association and translational fidelity were increased to the same level. Computer modeling was used to analyze the effect of the mutations in helix 24 on the interaction between the tetraloop and its receptor. This study demonstrates the functional importance of the interaction between the 900 tetraloop and helix 24.

Original languageEnglish (US)
Pages (from-to)683-693
Number of pages11
JournalJournal of Molecular Biology
Issue number4
StatePublished - May 7 2004
Externally publishedYes


  • CAT, chloramphenicol acetyltransferase
  • GFP, green fluorescent protein
  • IPTG, isopropyl-β-D- thiogalactopyranoside
  • Instant evolution
  • Ribosomal RNA
  • Ribosomal subunit association
  • Tetraloop/receptor interaction
  • Translational fidelity

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology


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