Crystallization of RNA and RNA-protein complexes.

RNA plays a direct role in a variety of cellular activities, and in many cases its biological function is conferred by the RNA three-dimensional structure. X-ray crystallography is the method of choice for determining high resolution structures of large RNA molecules, and can also be used to compare related RNAs and identify conformational changes that may accompany biochemical activity. However, crystallization remains the rate-limiting step in RNA structure determination due to the difficulty in obtaining well-ordered crystals for X-ray diffraction analysis. Several approaches to sample preparation, crystallization, and crystal handling are presented that have been used successfully in the structure determination of RNA and RNA-protein complexes in our laboratory, and should be generally applicable to RNAs in other systems.