Projects . ... Chemical probing of tmRNA structure in ribosomal complexes blocked at different stages of trans-translation allowed us to follow the structural changes starting from early steps of tmRNA passage, with the TLD in tmRNA at the ribosomal E-site, up to the termination step of trans-translation. ... We propose that SmpB remains bound to TLD of tmRNA starting from the second codon at the ribosomal A-site, when TLD is at the ribosomal E-site, up to trans-translation termination. ...