Solution structure and dynamics of a designed monomeric variant of the lambda Cro repressor

Area of Science:

• Molecular biology
• Structural biology
• Biophysics

Background:

• The lambda Cro repressor is a key protein in bacteriophage lambda genetic regulation.
• Understanding its structure-function relationship is crucial for gene regulation studies.

Purpose of the Study:

• To determine the solution structure and dynamics of a monomeric variant of the lambda Cro repressor.
• To investigate the structural impact of inserting five amino acids at the dimer interface.

Main Methods:

• Multidimensional Nuclear Magnetic Resonance (NMR) spectroscopy was employed.
• Structure calculation utilized hybrid distance geometry/simulated annealing with NOE-distance, hydrogen-bond, and dihedral-angle restraints.

Main Results:

• The solution structure of the monomeric Cro variant (Cro K56[DGEVK]) was determined with high precision.
• The inserted residues formed a beta hairpin, consistent with design, but turns were not well-defined.
• Dynamics studies indicated flexibility in specific regions, including the engineered turn.

Conclusions:

• The engineered Cro repressor variant maintains its overall designed structure in solution.
• Flexibility in specific regions, particularly turns, may be important for DNA recognition.
• NMR provides insights into protein dynamics and conformational variation relevant to DNA binding proteins.