STRUCTURE AND FUNCTION OF RNA-MODIFYING PROTEINS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Introducing modifications to bases in RNA has been identified as an important mechanism for diversification of proteins encoded in the genomes of various organisms. Numerous deaminases have been identified that catalyze direct changes to nucleobases in tRNA, mRNA, and even viral RNA. Such proteins are required for generating antibody diversity, innate cellular responses to invading viruses, as well as introducing tRNA degeneracy for recognition of multiple codons with a single tRNA during translation. The focus of the current research is to study the chemical mechanism of adenosine deaminases that modify specific sites in RNA. We are focusing our current studies on TadA, an enzyme from bacteria that introduces inosines at the wobble position at the anticodon position of a specific tRNA. The approach is to generate novel structures of these enzymes bound to target RNA using X-ray crystallography. Present experiments are designed to allow the visualization of how this protein recognizes and carries out the chemical modification of RNA by crystallizing the protein with RNA intermediates representing distinct steps along the reaction pathway. These results will have implications for RNA recognition and catalysis by other closely related deaminases that act on DNA and RNA.