Determining structures of RNA aptamers and riboswitches by X-ray crystallography.

Structural biology plays a central role in gaining a full understanding of the myriad roles of RNA in biology. In recent years, innovative approaches in RNA purification and crystallographic methods have lead to the visualization of an increasing number of unique structures, providing new insights into its function at the atomic level. This article presents general protocols which have streamlined the process of obtaining a homogeneous sample of properly folded and active RNA in high concentrations that crystallizes well in the presence of a suitable heavy-atom for phasing. Of particular importance are approaches toward RNA crystallography that include exploring "construct space" as opposed to "condition space". Moreover, development of a highly flexible method for experimentally phasing RNA crystals may open the door to a relatively simple means of solving these structures.