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Refined structure of Cro repressor protein from bacteriophage lambda suggests both flexibility and plasticity
D H Ohlendorf1, D E Tronrud, B W Matthews
1Institute of Molecular Biology Howard Hughes Medical Institute and Department of Physics, University of Oregon, Eugene, OR, 97403-1229, USA.
Journal of Molecular Biology
|July 7, 1998
Summary
Refined X-ray crystallography of the Cro repressor protein from phage lambda reveals its structure and flexibility. This protein dimer exhibits flexibility crucial for DNA binding, with NMR data showing good agreement but some variations in solution structure.
Area of Science:
- Molecular biology
- Structural biology
- Biophysics
Background:
- The Cro repressor protein from phage lambda plays a critical role in viral gene regulation.
- Understanding its structure and dynamics is essential for deciphering its interaction with DNA.
Purpose of the Study:
- To refine the crystal structure of the Cro repressor protein.
- To compare its structure with NMR data and investigate its flexibility.
- To elucidate the mechanisms underlying its thermal stability.
Main Methods:
- X-ray crystallography at 2.3 A resolution.
- Nuclear Magnetic Resonance (NMR) spectroscopy.
- Structural comparison and analysis.
Main Results:
- The refined Cro repressor structure supports previous findings and highlights subunit plasticity and dimer flexibility, important for DNA complex formation.
- NMR data shows reasonable agreement with crystal structure, but variations in dimer models limit definitive comparison of solution and crystal structures.
- The refined structure suggests Tyr26 is equally solvent-exposed in folded and unfolded states, challenging the "reverse hydrophobic effect" hypothesis.
- The Tyr26-->Asp substitution enhances stability, potentially through interaction with an alpha-helix dipole.
Conclusions:
- The Cro repressor protein exhibits significant flexibility, crucial for its function in DNA binding.
- The refined structure provides insights into the molecular basis of Cro repressor stability and interactions.
- Further studies are needed to fully reconcile X-ray and NMR structural data in solution.