Hinge-helix formation and DNA bending in various lac repressor-operator complexes.

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• The lac operon is regulated by the lac repressor protein.
• The hinge region of the lac repressor is crucial for DNA binding and operon regulation.
• Previous studies questioned whether the lac repressor bends the wild-type operator DNA.

Purpose of the Study:

• To investigate the role of the lac repressor's hinge region in wild-type operator binding.
• To determine if the lac repressor bends wild-type operator DNA.
• To elucidate the function of the central base-pair in repressor-operator interactions.

Main Methods:

• Structural analysis of lac repressor-operator complexes.
• DNA-protein interaction studies.
• Biophysical techniques to assess DNA bending and binding affinities.

Main Results:

• The lac repressor forms hinge-helices and bends wild-type operator DNA, similar to symmetric operators.
• Differences in DNA binding domain interactions with operator half-sites were observed.
• The central base-pair of the wild-type operator plays a significant role in repressor binding.

Conclusions:

• The lac repressor's hinge helices are formed in wild-type complexes, inducing DNA bending.
• A model was developed explaining repressor affinity for various lac operator sequences based on half-site binding differences and spacer lengths.