title: Transfer-messenger RNA unfolds as it transits the ribosome.
abstract: In bacteria, translation of mRNAs lacking stop codons produces truncated polypeptides and traps ribosomes in unproductive complexes. Potentially harmful truncated proteins are tagged with short peptides encoded by the mRNA-like domain of tmRNA and targeted for digestion by housekeeping proteases. We show that altered Escherichia coli transfer-messenger RNAs (tmRNAs) produce in vivo fusion proteins with peptide tags that extend far beyond the conventional termination signal of the wild-type tmRNA. Regions of tmRNA capable of serving as templates for protein synthesis include helix 5, as well as pseudoknots 2, 3, and 4. The removal of all six in-frame stop codons negatively affects tmRNA processing, thereby preventing translation of the 3' portion of the tRNA-like domain. These findings provide evidence that trans-translation can be accompanied by the unfolding of significant portions of the tmRNA molecule. Many of these conformational changes are likely to be required during trans-translation to maintain the ribosomal subunits in close proximity to the tmRNA for monitoring its transit.
authors.affiliation: Department of Animal Sciences, Auburn University, 210 Upchurch Hall, Auburn, AL 36849-5415, USA.
authors.forename: Iwona K
authors.initials: IK
authors.lastname: Wower
authors.forename: Christian
authors.initials: C
authors.lastname: Zwieb
authors.forename: Jacek
authors.initials: J
authors.lastname: Wower
mesh_terms: D001483:Base Sequence; D018388:Codon, Terminator / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D009154:Mutation / Q000235:genetics; D009690:Nucleic Acid Conformation; D010443:Peptide Chain Termination, Translational; D014176:Protein Biosynthesis; D012329:RNA, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism*
chemical_list: D018388:Codon, Terminator; D012329:RNA, Bacterial; C096222:tmRNA