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Trans-translation by tmRNA and SmpB
Masataka Une1, Daisuke Kurita, Akira Muto
1Department of Biochemistry and Molecular Biology, Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, Aomori 036-8561, Japan.
Nucleic Acids Symposium Series (2004)
|September 15, 2009
Summary
Bacterial tmRNA and SmpB protein bind to the ribosome during trans-translation. This molecular mimicry explains how tmRNA recognizes stalled ribosomes and bypasses codon-anticodon interactions.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- tmRNA functions as both tRNA and mRNA, facilitating trans-translation.
- Trans-translation allows ribosomes to switch from problematic mRNAs to tmRNA.
- SmpB protein is essential for tmRNA binding to the ribosome.
Purpose of the Study:
- To investigate the interaction between SmpB, tmRNA, and the ribosome.
- To elucidate the binding sites and orientation of SmpB within the ribosome.
- To understand the mechanism of tmRNA recognition and ribosome rescue.
Main Methods:
- Directed hydroxyl radical probing was employed.
- Analysis of SmpB binding sites on the 30S ribosomal subunit.
- Mapping the location of SmpB C-terminal regions relative to mRNA path.
Main Results:
- Two distinct SmpB binding sites were identified at the ribosomal A-site and P-site.
- The C-terminal regions of SmpB were found along the mRNA path within the 30S subunit.
- Evidence supports a molecular mimicry mechanism involving both tmRNA and SmpB.
Conclusions:
- A novel molecular mimicry model is proposed for trans-translation.
- tmRNA and SmpB mimic tRNA and mRNA structures/functions.
- This mechanism explains tmRNA's preferential binding to stalled ribosomes and the absence of codon-anticodon interaction.
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