View the Current Issue

Article

  • The EMBO Journal (2007) 26, 2421 - 2431
  • doi:10.1038/sj.emboj.7601677

Published online: 19 April 2007

Structures of modified eEF2dot80S ribosome complexes reveal the role of GTP hydrolysis in translocation

Derek J Taylor1, Jakob Nilsson2,a, A Rod Merrill3, Gregers Rom Andersen2, Poul Nissen2 and Joachim Frank1,4

  1. Howard Hughes Medical Institute, Health Research Inc., at the Wadsworth Center, Albany, NY, USA
  2. Macromolecular Crystallography, Department of Molecular Biology, University of Aarhus, Århus, Denmark
  3. Department of Molecular and Cellular Biology, University of Guelph, Ontario, Canada
  4. Department of Biomedical Sciences, University at Albany, Albany, NY, USA

Correspondence to:

Joachim Frank, Howard Hughes Medical Institute, Health Research Inc., at the Wadsworth Center, Empire State Plaza, Albany, NY, 12201-0509 USA. Tel.: +1 518 474 7002; Fax: +1 518 486 2191; E-mail: joachim@wadsworth.org

aPresent address: The Wellcome Trust and Cancer Research UK Gurdon Institute, The Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK

Received 27 September 2006; Accepted 15 March 2007

On the basis of kinetic data on ribosome protein synthesis, the mechanical energy for translocation of the mRNA–tRNA complex is thought to be provided by GTP hydrolysis of an elongation factor (eEF2 in eukaryotes, EF-G in bacteria). We have obtained cryo-EM reconstructions of eukaryotic ribosomes complexed with ADP-ribosylated eEF2 (ADPR-eEF2), before and after GTP hydrolysis, providing a structural basis for analyzing the GTPase-coupled mechanism of translocation. Using the ADP-ribosyl group as a distinct marker, we observe conformational changes of ADPR-eEF2 that are due strictly to GTP hydrolysis. These movements are likely representative of native eEF2 motions in a physiological context and are sufficient to uncouple the mRNA–tRNA complex from two universally conserved bases in the ribosomal decoding center (A1492 and A1493 in Escherichia coli) during translocation. Interpretation of these data provides a detailed two-step model of translocation that begins with the eEF2/EF-G binding-induced ratcheting motion of the small ribosomal subunit. GTP hydrolysis then uncouples the mRNA–tRNA complex from the decoding center so translocation of the mRNA–tRNA moiety may be completed by a head rotation of the small subunit.

  • Keywords:

    • cryo-EM,
    • EF-G,
    • elongation,
    • GTPase,
    • Switch 1