Open AccessIntersubunit movement is required for ribosomal translocation
Author(s) -
Lucas H. Horan,
Harry F. Noller
Publication year - 2007
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.0700762104
Subject(s) - ribosome , eukaryotic ribosome , 50s , ribosomal rna , chromosomal translocation , protein subunit , 30s , protein biosynthesis , ribosomal protein , biophysics , eukaryotic large ribosomal subunit , chemistry , biology , microbiology and biotechnology , biochemistry , eukaryotic small ribosomal subunit , rna , gene
Translocation of tRNA and mRNA during protein synthesis is believed to be coupled to structural changes in the ribosome. The “ratchet model,” based on cryo-EM reconstructions of ribosome complexes, invokes relative movement of the 30S and 50S ribosomal subunits in this process; however, evidence that directly demonstrates a requirement for intersubunit movement during translocation is lacking. To address this problem, we created an intersubunit disulfide cross-link to restrict potential movement. The cross-linked ribosomes were unable to carry out polypeptide synthesis; this inhibition was completely reversed upon reduction of the disulfide bridge.In vitro assays showed that the cross-linked ribosomes were specifically blocked in elongation factor G-dependent translocation. These findings show that intersubunit movement is required for ribosomal translocation, accounting for the universal two-subunit architecture of ribosomes.