RT Journal Article SR Electronic T1 GTP Hydrolysis by eIF5B in the Last Step of Translation Initiation Is Activated by a Rotation of the Small Ribosomal Subunit JF bioRxiv FD Cold Spring Harbor Laboratory SP 172825 DO 10.1101/172825 A1 Israel S. Fernández A1 V. Ramakrishnan YR 2017 UL http://biorxiv.org/content/early/2017/08/04/172825.abstract AB Placement of an initiator aminoacyl-tRNA [(f)Met-tRNAi(f)Met] base paired with the AUG initiation codon of a messenger RNA (mRNA) is the first step of translation. The eukaryotic translation factor eIF5B or its bacerial homologue IF2 facilitate the correct positioning of initiator tRNA in the P site of the ribosome. We report the electron cryomicroscopy (cryoEM) structure of a stabilized intermediate state of a yeast 80S/tRNAiMet/eIF5B complex at 3.6 Å resolution. The structure shows how a universally conserved tyrosine couples the rotational state of the small ribosomal subunit with GTP hydrolysis.