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An operator-induced conformational change in the C-terminal domain of the lambda repressor
R Saha1, U Banik, S Bandopadhyay
1Department of Biophysics, Bose Institute, Calcutta, India.
The Journal of Biological Chemistry
|March 25, 1992
Summary
The fluorescent probe Bis-ANS binds to lambda repressor's C-terminal domain, with binding cooperativity influenced by protein aggregation. Operator binding induces conformational changes in the repressor's C-terminal domain, affecting fluorescence.
Area of Science:
- Molecular Biology
- Biophysics
Background:
- Lambda repressor regulates phage gene expression.
- Understanding repressor-operator interactions is key to gene regulation studies.
Purpose of the Study:
- To investigate the binding mechanism of Bis-ANS to lambda repressor.
- To explore operator-induced conformational changes in lambda repressor.
Main Methods:
- Fluorescence spectroscopy using Bis-ANS and tryptophan fluorescence.
- Protein concentration-dependent binding studies.
Main Results:
- Bis-ANS binds to the C-terminal domain of lambda repressor with positive cooperativity.
- Binding cooperativity is dependent on repressor concentration and favors the dimeric form.
- Operator OR1 binding enhances Bis-ANS fluorescence and quenches tryptophan fluorescence, indicating conformational changes in the C-terminal domain.
Conclusions:
- Operator binding induces significant conformational changes in the lambda repressor's C-terminal domain.
- These conformational changes, detected by fluorescence probes, are crucial for repressor function.