Crystallogenesis at the Heart of the Interplay between Science and Technology in the Quest to Comprehend tRNA Biology

Transfer RNAs (tRNA) are small RNAs that provide the interface between DNA and ribosome-dependent protein synthesis, besides being involved in many other cellular processes. They interact with an impressive number of small molecule and macromolecular ligands and show structural and functional plasticity far to be deciphered. Here it is shown how tRNA biology was (and still is) idea and technology-driven and why crystallogenesis was at the heart of this science/technology interplay. Thus the quest to understand tRNA recognition/misrecognition by aminoacyl-tRNA synthetases (aaRS) stimulated biologists since the 1960s to crystallize tRNAs and their protein partners under their different functional states. This led to novel crystallization methods (vapor phase diffusion, microdialysis), characterization of system-specific additives (polyamines, metal ions, adenylate analogues), and discovery of ammonium sulfate as a crystallant for tRNA:aaRS complexes. Studies on the physical chemistry of tRNA and aaRS crystal growth, including the role of microgravity, were undertaken, and advanced methods for optimizing crystal quality were validated. As a result, the empiricism in tRNA crystallization was replaced by more rationality and led to the discipline of crystallogenesis. This facilitated tRNA crystallography, culminating with tRNA on the ribosome, thereby providing a robust structural background to better comprehend tRNA biology.