Nature Structural & Molecular Biology 11, 1054–1059 (2004); published online 24 October 2004; corrected after print 20 March 2007

In the version of this article initially published, the PDB codes were incorrect. The correct codes for the protein Y bound ribosome are 1VOQ, 1VOS, 1VOV, 1VOX, 1VOZ for the 30S and 1VOR, 1VOU, 1VOW, 1VOY and 1VP0 for the 50S. The error has been corrected in the HTML and PDF versions of this article.