Crystallization of protein-DNA complexes.

Determining the crystal structure of a protein-DNA complex can provide a wealth of information regarding protein function and mechanism. The foundation for all successful X-ray structure determination is the ability to produce diffraction-quality crystals. Crystallization of protein-DNA complexes often presents unique challenges because of the additional parameters involved. This chapter will outline many of those challenges, including choice of DNA and formation of a stable protein-DNA complex and provide guidance in preparing for crystallization experiments. Additionally, techniques for oligonucleotide purification, sample preparation, and crystallization methods are provided. Careful thought and initial analysis of the protein-DNA complex prior to crystallization experiments followed by optimization of crystallization parameters can greatly increase the likelihood of producing well-diffracting crystals.