The Ternary Complex of EF-Tu and Its Role in Protein Biosynthesis

The past year has seen a breakthrough in our structural understanding of how aminoacyl-tRNAs are selected and transported to the ribosomal A-site in order to decode genetic information contained in messenger RNA. All aminoacyl-tRNAs are recognized by the elongation factor EF-Tu in prokaryotes or EF-1alpha in eukaryotes. The recent determination of the structure of the ternary complex of aminoacyl-tRNA, EF-Tu and a GTP analogue shows how the CCA end of all aminoacyl-tRNA structures can be accommodated in a specific binding site on EF-Tu-GTP, and how part of the T-helix can be recognized by EF-Tu in a non-sequence-specific way. Furthermore, the structure of the ternary complex shows striking structural similarity to the structure of another prokaryotic elongation factor, EF-G, the tRNA translocase, in its GDP or empty form. This observation has led to the proposal of a general macromolecular mimicry of RNA and protein, which predicts elements of RNA-like structures will occur in other translation factors, such as initiation factors and release factors, that interact with similar sites on the ribosome.