GTPases IF2 and EF-G bind GDP and the SRL RNA in a mutually exclusive manner

Sci Rep. 2012;2:843. doi: 10.1038/srep00843. Epub 2012 Nov 13.


Translational GTPases (trGTPases) are involved in all four stages of protein biosynthesis: initiation, elongation, termination and ribosome recycling. The trGTPases Initiation Factor 2 (IF2) and Elongation Factor G (EF-G) respectively orchestrate initiation complex formation and translocation of the peptidyl-tRNA:mRNA complex through the bacterial ribosome. The ribosome regulates the GTPase cycle and efficiently discriminates between the GDP- and GTP-bound forms of these proteins. Using Isothermal Titration Calorimetry, we have investigated interactions of IF2 and EF-G with the sarcin-ricin loop of the 23S rRNA, a crucial element of the GTPase-associated center of the ribosome. We show that binding of IF2 and EF-G to a 27 nucleotide RNA fragment mimicking the sarcin-ricin loop is mutually exclusive with that of GDP, but not of GTP, providing a mechanism for destabilization of the ribosome-bound GDP forms of translational GTPases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteria / metabolism
  • Bacterial Proteins / metabolism*
  • Guanosine Triphosphate / metabolism*
  • Peptide Elongation Factor G / metabolism*
  • Prokaryotic Initiation Factor-2 / metabolism*
  • Protein Binding
  • RNA, Messenger / metabolism
  • RNA, Ribosomal, 23S / metabolism
  • RNA, Transfer, Amino Acyl / metabolism
  • Ribosomes / metabolism


  • Bacterial Proteins
  • Peptide Elongation Factor G
  • Prokaryotic Initiation Factor-2
  • RNA, Messenger
  • RNA, Ribosomal, 23S
  • RNA, Transfer, Amino Acyl
  • tRNA, peptidyl-
  • Guanosine Triphosphate