PMID:15547251
| Citation |
Singh, NS and Varshney, U (2004) A physiological connection between tmRNA and peptidyl-tRNA hydrolase functions in Escherichia coli. Nucleic Acids Res. 32:6028-37 |
|---|---|
| Abstract |
The bacterial ssrA gene codes for a dual function RNA, tmRNA, which possesses tRNA-like and mRNA-like regions. The tmRNA appends an oligopeptide tag to the polypeptide on the P-site tRNA by a trans-translation process that rescues ribosomes stalled on the mRNAs and targets the aberrant protein for degradation. In cells, processing of the stalled ribosomes is also pioneered by drop-off of peptidyl-tRNAs. The ester bond linking the peptide to tRNA is hydrolyzed by peptidyl-tRNA hydrolase (Pth), an essential enzyme, which releases the tRNA and the aberrant peptide. As the trans-translation mechanism utilizes the peptidyl-transferase activity of the stalled ribosomes to free the tRNA (as opposed to peptidyl-tRNA drop-off), the need for Pth to recycle such tRNAs is bypassed. Thus, we hypothesized that tmRNA may rescue a defect in Pth. Here, we show that overexpression of tmRNA rescues the temperature-sensitive phenotype of Escherichia coli (pth(ts)). Conversely, a null mutation in ssrA enhances the temperature-sensitive phenotype of the pth(ts) strain. Consistent with our hypothesis, overexpression of tmRNA results in decreased accumulation of peptidyl-tRNA in E.coli. Furthermore, overproduction of tmRNA in E.coli strains deficient in ribosome recycling factor and/or lacking the release factor 3 enhances the rescue of pth(ts) strains. We discuss the physiological relevance of these observations to highlight a major role of tmRNA in decreasing cellular peptidyl-tRNA load. |
| Links |
PubMed PMC534616 Online version:10.1093/nar/gkh924 |
| Keywords |
Alleles; Carboxylic Ester Hydrolases/genetics; Carboxylic Ester Hydrolases/metabolism; Carboxylic Ester Hydrolases/physiology; Escherichia coli/enzymology; Escherichia coli/genetics; Escherichia coli/metabolism; Escherichia coli Proteins/genetics; Mutation; Peptide Termination Factors/genetics; Phenotype; Promoter Regions, Genetic; RNA, Bacterial/genetics; RNA, Bacterial/metabolism; RNA, Bacterial/physiology; RNA, Transfer, Amino Acyl/metabolism; Temperature |
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