tmRNA rescues stalled ribosomes in eubacteria by forcing the ribosome to abandon its mRNA template and resume translation with tmRNA itself as a template. Pseudoknot 1 (pk1), immediately upstream of this coding region in tmRNA, is a structural element that is considered essential for tmRNA function based on the analysis of pk1 mutants in vitro. pk1 binds near the ribosomal decoding site and may...

The small, stable RNA molecule encoded by ssrA, known as tmRNA or 10Sa RNA, is required for the growth of certain hybrid limm phages in Escherichia coli. tmRNA has been shown to tag partially synthesized proteins for degradation in vivo by attaching a short peptide sequence, encoded by tmRNA, to the carboxyl termini of these proteins. This tag sequence contains, at its C terminus, an amino acid...

Genes for the RNA tmRNA and protein SmpB, partners in the trans-translation process that rescues stalled ribosomes, have previously been found in all bacteria and some organelles. During a major update of The tmRNA Website (relocated to http://bioinformatics.sandia.gov/tmrna), including addition of an SmpB sequence database, we found some bacteria that lack functionally significant regions of S...

The bacterial ribosome switches from an mRNA lacking an in-frame stop codon and resumes translation on a specialized RNA known as tmRNA, SsrA or 10Sa RNA. We find that the ribosome can reach and use the extreme 3' terminal codon of the defective mRNA prior to switching. The first triplet to be translated in tmRNA (the resume codon) is determined at two levels: distant elements in tmRNA restrict...

The tmRNA database (tmRDB) is maintained at the University of Texas Health Science Center at Tyler, Texas, and is accessible on the WWW at URL http://psyche.uthct.edu/dbs/tmRDB/tmRDB.++ +html. A tmRDB mirror site is located on the campus of Auburn University, Auburn, Alabama, reachable at the URL http://www.ag.auburn.edu/mirror/tmRDB/. Since April 1997, the tmRDB has provided sequences of tmRNA...

Bacterial ribosomes stalled on defective messenger RNAs (mRNAs) are rescued by tmRNA, an approximately 300-nucleotide-long molecule that functions as both transfer RNA (tRNA) and mRNA. Translation then switches from the defective message to a short open reading frame on tmRNA that tags the defective nascent peptide chain for degradation. However, the mechanism by which tmRNA can enter and move ...

tmRNA, through its tRNA and mRNA properties, adds short peptide tags to abnormal proteins, targeting these proteins for proteolytic degradation. Although the conservation of tmRNA throughout the bacterial kingdom suggests that it must provide a strong selective advantage, it has not been shown to be essential for any bacterium. We report that tmRNA is essential in Neisseria gonorrhoeae. Althoug...

The tmRNA-SmpB system releases ribosomes stalled on truncated mRNAs and tags the nascent polypeptides to target them for proteolysis. In many species, mutations that disrupt tmRNA activity cause defects in growth or development. In Caulobacter crescentus cells lacking tmRNA activity there is a delay in the initiation of DNA replication, which disrupts the cell cycle. To understand the molecular...

The tmRNA system performs translational surveillance and ribosome rescue in all eubacteria and some eukaryotic organelles. This system intervenes when ribosomes read to the 3' end of an mRNA or pause at internal codons with subsequent mRNA cleavage. A complex of alanyl-tmRNA (which functions as a tRNA and mRNA), SmpB protein, and EF-TucGTP binds stalled ribosomes, the nascent polypeptide is tra...

Ribosomes mediate protein synthesis by decoding the information carried by messenger RNAs (mRNAs) and catalysing peptide bond formation between amino acids. When bacterial ribosomes stall on incomplete messages, the trans-translation quality control mechanism is activated by the transfer-messenger RNA bound to small protein B (tmRNA-SmpB ribonucleoprotein complex). Trans-translation liberates t...