Xabier Agirrezabala, Hstau Liao, Eduard Schreiner, Jie Fu, Rodrigo Ortiz-Meoz,
Klaus Schulten, Rachel Green, and Joachim Frank.
Structural characterization of mRNA-tRNA translocation
intermediates.
Proceedings of the National Academy of Sciences, USA,
109:6094-6099, 2012.
AGIR2012
Analysis of a wild-type E. coli pre-translocational sample competent for unimpaired
forward translocation by cryo-EM, classification, and single-particle reconstruction has
revealed the presence of previously unseen intermediate substates of the bacterial
ribosome during the first phase of translocation, characterized by intermediate
intersubunit rotations, L1 stalk positions, and tRNA configurations. Furthermore, we have
described the domain rearrangements in quantitative terms, which has allowed us to
define the processivity and coordination of the conformational reorganization of the
ribosome, along with the associated changes in tRNA ribosome-binding configuration.
The observed occupancies of substates also allowed a profile of the free-energy landscape
to be reconstructed. The results are consistent with the view of the ribosome as a
molecular machine employing Brownian motion to reach a functionally productive state
(“macrostate II”) via a series of substates with incremental changes in conformation.
