Preparation and crystallization of dynamic NF-kappa B.Ikappa B complexes

Area of Science:

• Structural Biology
• X-ray Crystallography
• Protein Crystallization

Background:

• X-ray crystallography demands well-diffracting crystals for molecular structure determination.
• Biological macromolecules with internal flexibility or self-association pose crystallization challenges.
• Stabilizing ligands and removal of flexible regions can enhance crystal formation.

Purpose of the Study:

• To determine the crystal structure of the Rel homology region of transcription factor NF-kappaB.
• To investigate crystallization strategies for NF-kappaB in complex with its inhibitors IkappaBalpha and IkappaBbeta.
• To overcome crystallization obstacles presented by protein flexibility and self-association.

Main Methods:

• Applied principles of protein stabilization and ligand addition for crystallization.
• Utilized recombinant overexpression for truncated IkappaBalpha, selecting the correct start site.
• Developed purification and complex formation protocols for NF-kappaB.IkappaBalpha and NF-kappaB.IkappaBbeta complexes.

Main Results:

• Successfully formed well-diffracting crystals of NF-kappaB.IkappaBalpha complex under stringent conditions.
• Achieved crystal formation for NF-kappaB.IkappaBbeta complex by adapting methods used for IkappaBalpha.
• Demonstrated that neither NF-kappaB nor its inhibitors crystallize independently.

Conclusions:

• Protein stabilization via inhibitor complexation is crucial for crystallizing flexible molecules like NF-kappaB.
• The strategy of using stabilizing ligands is effective for obtaining crystals of protein complexes.
• Successful crystallization of NF-kappaB complexes provides a basis for X-ray crystallography structure determination.