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Genetic selection for mutations that impair the co-operative binding of lambda repressor
N Benson1, C Adams, P Youderian
1Department of Biological Sciences, University of Southern California, Los Angeles 90089-1481.
Molecular Microbiology
|February 1, 1994
Summary
Mutant bacteriophage lambda repressors were identified that lose cooperative binding to DNA but retain single-site binding. This research advances understanding of protein-DNA interactions and regulatory complex assembly.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Bacteriophage lambda repressor protein is crucial for regulating viral gene expression.
- This repressor exhibits cooperative binding to adjacent DNA target sites, a key feature for its function.
Purpose of the Study:
- To isolate and characterize mutant lambda repressors with altered DNA binding properties.
- To investigate the molecular basis of cooperative binding in protein-DNA interactions.
Main Methods:
- Utilized a novel combination of positive genetic selections with P22 challenge phage operon fusions.
- Generated and analyzed mutant lambda repressors exhibiting specific binding defects.
Main Results:
- Identified mutations (cb mutations) affecting cooperative binding to tandem DNA sites.
- These mutations lead to 10 distinct amino acid changes, pinpointing eight residues in the repressor's carboxyl-terminus.
- Mutants retained the ability to bind to strong, single DNA sites.
Conclusions:
- The carboxyl-terminus of lambda repressor plays a critical role in cooperative DNA binding.
- The genetic selection strategy is broadly applicable for studying other protein-DNA interactions and regulatory complex assembly.