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Mutations that alter initiation codon discrimination by Escherichia coli initiation factor IF3.
C Sacerdot1, E de Cock, K Engst
1Institut de Biologie Physico-Chimique, UPR9073 du CNRS, 13 rue Pierre et Marie Curie, Paris, 75005, France.
Journal of Molecular Biology
|May 18, 1999
Summary
Researchers isolated mutations in the infC gene, affecting initiation factor 3 (IF3) protein function. Some mutants showed impaired discrimination of initiation codons and altered ribosomal subunit binding, revealing insights into IF3
Area of Science:
- Molecular Biology
- Genetics
- Protein Biochemistry
Background:
- Initiation factor 3 (IF3) is crucial for bacterial translation initiation.
- IF3 plays a role in selecting the correct start codon and ensuring ribosomal subunit association.
Purpose of the Study:
- To isolate and characterize mutations in the infC gene affecting IF3 function.
- To investigate the impact of these mutations on translation initiation fidelity and ribosomal binding.
Main Methods:
- Genetic screens for infC mutations.
- Complementation assays to assess IF3 function.
- Analysis of initiation codon discrimination.
- Ribosomal subunit binding assays (30S and 50S).
Main Results:
- Seven stable IF3 variants with impaired function were isolated.
- Mutants exhibited defects in discriminating non-canonical initiation codons (AUU, ACG).
- Two mutants showed significant defects in complementation and codon discrimination, with altered 30S subunit binding.
Conclusions:
- Mutations in the C-terminal domain of IF3 can disrupt its function.
- Altered ribosomal subunit binding, including non-specific interactions, can lead to translation defects.
- Specific acidic residues may play a role in preventing non-cognate RNA interactions.