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Mapping the lacZ ribosome binding site by RNA footprinting
1Department of Microbiology, University of California, Los Angeles 90024-1489.
Biochemistry
|October 3, 1989
Summary
This study used RNA footprinting to map ribosome interactions on Escherichia coli lacZ mRNA. Ribosomes protect specific sites, including the Shine-Dalgarno region and initiation codon, revealing selective mRNA binding.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The ribosome binding site (RBS) on mRNA is crucial for initiating protein synthesis.
- Understanding RBS-ribosome interactions provides insights into gene expression regulation.
- Escherichia coli lacZ mRNA serves as a model system for studying translation initiation.
Purpose of the Study:
- To characterize the precise binding sites of ribosomes on Escherichia coli lacZ mRNA.
- To investigate the structural interactions between 70S ribosomes, fMet-tRNA, and mRNA during initiation.
Main Methods:
- RNA footprinting technique using RNA-reactive reagents and RNases.
- Incubation of purified E. coli 70S ribosomes and fMet-tRNA with lacZ mRNA.
- Mapping protected mRNA regions via primer extension with reverse transcriptase.
Main Results:
- A ~35-nucleotide region of the mRNA was protected by the ribosome.
- Protection was observed across the Shine-Dalgarno sequence and around the fMet initiation codon.
- An additional protected site was identified 7-12 nucleotides distal to the fMet codon, with enhanced reactivity.
Conclusions:
- Ribosome binding to mRNA is selective, involving specific interactions with multiple regions.
- The enhanced reactivity at the distal site suggests specific mRNA exposure or conformational changes.
- These findings elucidate the mechanism of translation initiation in E. coli.