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Summary
The lac repressor protein
Area of Science:
- Molecular biology
- Biophysics
Background:
- The lac repressor protein controls gene expression by binding to the lac operator.
- Inducers like IPTG disrupt this binding, altering gene expression.
- The N-terminal residues of the repressor are crucial for DNA binding.
Purpose of the Study:
- To investigate the structural organization of the lac repressor and its interaction with DNA.
- To determine the spatial arrangement of repressor headpieces relative to the core.
Main Methods:
- Neutron scattering with contrast variation was employed.
- Measurements were performed on the intact protein, its tryptic core, and complexes with IPTG.
Main Results:
- Repressor headpieces are positioned significantly far from the core's center of mass (67 +/- 10 A).
- The inducer (IPTG) binding does not substantially alter the protein's overall radius of gyration.
Conclusions:
- The study provides insights into the structural basis of lac repressor-DNA interaction.
- The spatial separation of headpieces from the core is a key feature of the repressor's functional architecture.