E. coli elongation factor Tu bound to a GTP analogue displays an open conformation equivalent to the GDP-bound form

Nucleic Acids Res. 2018 Sep 19;46(16):8641-8650. doi: 10.1093/nar/gky697.

Abstract

According to the traditional view, GTPases act as molecular switches, which cycle between distinct 'on' and 'off' conformations bound to GTP and GDP, respectively. Translation elongation factor EF-Tu is a GTPase essential for prokaryotic protein synthesis. In its GTP-bound form, EF-Tu delivers aminoacylated tRNAs to the ribosome as a ternary complex. GTP hydrolysis is thought to cause the release of EF-Tu from aminoacyl-tRNA and the ribosome due to a dramatic conformational change following Pi release. Here, the crystal structure of Escherichia coli EF-Tu in complex with a non-hydrolysable GTP analogue (GDPNP) has been determined. Remarkably, the overall conformation of EF-Tu·GDPNP displays the classical, open GDP-bound conformation. This is in accordance with an emerging view that the identity of the bound guanine nucleotide is not 'locking' the GTPase in a fixed conformation. Using a single-molecule approach, the conformational dynamics of various ligand-bound forms of EF-Tu were probed in solution by fluorescence resonance energy transfer. The results suggest that EF-Tu, free in solution, may sample a wider set of conformations than the structurally well-defined GTP- and GDP-forms known from previous X-ray crystallographic studies. Only upon binding, as a ternary complex, to the mRNA-programmed ribosome, is the well-known, closed GTP-bound conformation, observed.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Crystallography, X-Ray
  • Escherichia coli / chemistry*
  • Escherichia coli / genetics
  • GTP Phosphohydrolases / chemistry
  • GTP Phosphohydrolases / genetics
  • Guanosine Diphosphate / chemistry
  • Guanosine Triphosphate / analogs & derivatives
  • Guanosine Triphosphate / chemistry*
  • Peptide Elongation Factor Tu / chemistry*
  • Peptide Elongation Factor Tu / genetics
  • Protein Biosynthesis / genetics
  • Protein Conformation*
  • RNA, Messenger / chemistry
  • RNA, Messenger / genetics
  • Ribosomes / chemistry
  • Ribosomes / genetics

Substances

  • RNA, Messenger
  • Guanosine Diphosphate
  • Guanosine Triphosphate
  • GTP Phosphohydrolases
  • Peptide Elongation Factor Tu