Crystallographic data for complexes of the Cro repressor with DNA

Area of Science:

• Molecular biology
• Structural biology
• Biophysics

Background:

• The bacteriophage lambda Cro repressor is a key protein regulating viral gene expression.
• Understanding Cro repressor-DNA interactions is crucial for deciphering viral life cycles.
• The lambda OR3 operator contains specific DNA sequences critical for repressor binding.

Purpose of the Study:

• To crystallize and characterize complexes of the bacteriophage lambda Cro repressor with specific DNA operator sequences.
• To obtain high-resolution structural data of these complexes for detailed molecular analysis.

Main Methods:

• Co-crystallization of the Cro repressor with two distinct DNA duplexes (lambda OR3 operator fragments).
• X-ray diffraction analysis to determine crystal space group and cell dimensions.
• Analysis of crystal contents to determine protein-DNA stoichiometry.

Main Results:

• Two distinct co-crystal forms were obtained, both belonging to the C2221 space group.
• Crystal cell dimensions were determined (a = 81.1 A, b = 89.2 A, c = 80.0 A).
• Stoichiometric analysis revealed approximately two hexamers per Cro dimer and one nonamer per dimer in the respective crystals, diffracting to ~3 A resolution.

Conclusions:

• The successful crystallization of Cro repressor-DNA complexes provides a foundation for detailed structural studies.
• These structures will elucidate the molecular mechanisms of bacteriophage lambda gene regulation.
• The findings pave the way for understanding repressor-DNA recognition at an atomic level.