The mechanism of translocation in e

The mechanism of translocation in eubacteria that we have suggested differs radically from all previous models [4,6,7,26,27] in that we propose the following: first, that EF-G enters the preT ribosome in the GDP-favoring form [16]; second, that EF-G•GDP drives the preT ribosome from its relaxed state with full binding sites for three tRNAs [5] to a twisted conformation with hybrid sites for two tRNAs [5]; and third, that exchange of GDP for GTP and an accompanying switch of the EF-G conformation from its GDP-bound to its GTP-bound structure occur on, rather than off, the ribosome.