Messenger RNA conformations in the ribosomal E site revealed by X‐ray crystallography

Abstract
A comparison of messenger RNA in X‐ray crystal structures of 70S ribosomal complexes in the initiation, post‐initiation and elongation states of translation shows distinct conformational differences in the exit (E) codon. Here, we present structural evidence indicating that, after the initiation event, the E codon nucleotides relax and form a classical A‐helical conformation. This conformation is similar to that of the P and A codons, and is favourable for establishing Watson–Crick interactions with the anticodon of E‐site transfer RNA.