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Probing the structure of gal operator-repressor complexes. Conformation change in DNA
1Laboratory of Molecular Biology, National Cancer Institute, Bethesda, Maryland 20892.
The Journal of Biological Chemistry
|September 25, 1987
Summary
The Gal repressor binds to two operator sites (OE and OI) in the gal operon, protecting specific DNA regions. This binding influences guanine reactivity, suggesting subunit interaction with DNA major grooves.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The gal operon's regulation involves the Gal repressor binding to operator sites OE and OI.
- Understanding repressor-DNA interactions is crucial for gene regulation studies.
Purpose of the Study:
- To precisely map the DNA regions protected by Gal repressor binding.
- To elucidate the molecular mechanism of Gal repressor-DNA interaction.
Main Methods:
- DNase I footprinting to identify protected DNA segments.
- Dimethyl sulfate methylation to probe DNA accessibility and repressor contacts.
Main Results:
- Identified ~22 bp protected regions in both OE and OI operators.
- Observed hindered methylation of specific guanines upon repressor binding.
- Demonstrated symmetrical binding consistent with a dimeric repressor.
Conclusions:
- Gal repressor likely contacts specific bases (1, 3, 1', 3') in the major groove.
- Repressor binding may alter DNA helical structure, affecting reactivity at other positions (8, 8').
- Supports a model where repressor subunits interact with distinct half-operator sites.