The ribosome in focus: new structures bring new insights.

Recent all-atom crystal structures of 70S ribosome functional complexes provide a detailed description of how the ribosome interacts with its mRNA and tRNA substrates. The structures support the view that the fundamental steps of translation are based on RNA-RNA interactions, which in some cases underwent further refinement as a result of having recruited proteins. The structural basis of the discrimination of cognate tRNA, the high affinity for tRNA in the peptidyl-tRNA site, the structure of the peptidyl transferase catalytic center, the specificity of the exit site for deacylated tRNA and other functional properties of the ribosome are now explained, confirmed or visualized for the first time in complexes containing full-length tRNAs and defined mRNAs. Clues to the structural dynamics of translation are suggested by conformational changes that occur in both tRNA and the ribosome upon complex formation.