Synthetic antibodies for accelerated RNA crystallography.

RNA structure is crucial to a wide range of cellular processes. The intimate relationship between macromolecular structure and function necessitates the determination of high-resolution structures of functional RNA molecules. X-ray crystallography is the predominant technique used for macromolecular structure determination; however, solving RNA structures has been more challenging than their protein counterparts, as reflected in their poor representation in the Protein Data Bank (<1%). Antibody-assisted RNA crystallography is a relatively new technique that promises to accelerate RNA structure determination by employing synthetic antibodies (Fabs) as crystallization chaperones that are specifically raised against target RNAs. Antibody chaperones facilitate the formation of ordered crystal lattices by minimizing RNA flexibility and replacing unfavorable RNA-RNA contacts with contacts between chaperone molecules. Atomic coordinates of these antibody fragments can also be used as search models to obtain phase information during structure determination. Antibody-assisted RNA crystallography has enabled the structure determination of 15 unique RNA targets, including 11 in the last 6 years. In this review, I cover the historical development of antibody fragments as crystallization chaperones and their application to diverse RNA targets. I discuss how the first structures of antibody-RNA complexes informed the design of second-generation antibodies and led to the development of portable crystallization modules that have greatly reduced the uncertainties associated with RNA crystallography. Finally, I outline unexplored avenues that can increase the impact of this technology in structural biology research and discuss potential applications of antibodies as affinity reagents for interrogating RNA biology outside of their use in crystallography. This article is categorized under: RNA Structure and Dynamics > RNA Structure, Dynamics and Chemistry RNA Interactions with Proteins and Other Molecules > Protein-RNA Recognition RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes.