| Título: | tmRNAs that encode proteolysis-inducing tags are found in all known bacterial genomes: A two-piece tmRNA functions in Caulobacter |
| Autores: |
Keiler, Kenneth C. Shapiro, Lucy Williams, Kelly P. |
| Fecha: | 2000-07-05 |
| Publicador: | The National Academy of Sciences |
| Fuente: |
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| Tipo: | Text |
| Tema: | Biological Sciences |
| Descripción: | A general mechanism in bacteria to rescue stalled ribosomes and to clear the cell of incomplete polypeptides involves an RNA species, tmRNA (SsrA), which functions as both a tRNA and an mRNA. This RNA encodes a peptide tag that is incorporated at the end of the aberrant polypeptide and targets it for proteolysis. We have identified a circularly permuted version of the tmRNA gene in α-proteobacteria as well as in a lineage of cyanobacteria. The genes in these two groups seem to have arisen from two independent permutation events. As a result of the altered genetic structure, these tmRNAs are composed of two distinct RNA molecules. The mature two-piece tmRNAs are predicted to have a tRNA-like domain and an mRNA-like domain similar to those of standard one-piece tmRNAs, with a break located in the loop containing the tag reading frame. A related sequence was found in the mitochondrial genome of Reclinomonas americana, but only the tRNA-like portion is retained. Although several sequence and structural motifs that are conserved among one-piece tmRNAs have been lost, the α-proteobacterium Caulobacter crescentus produces a functional two-piece tmRNA. |
| Idioma: | en |