Determination of an Intact Bacterial Group I Intron Structure by X-ray Crystallography

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The goal of this project is to obtain the high resolution X-ray crystal structure of an intact bacterial group I self-splicing intron. The crystallographic target is the intron from the purple bacterium Azoarcus. This intron is located in the anticodon loop of the pre-tRNA Ile. It is the smallest group I intron identified to date. Yet, it retains the conserved secondary and tertiary structural elements common to group I ribozymes and is exceptionally stable. The first goal of the project is to obtain the structure of a complex that retains all of its components, including the terminal G, the 5' and 3' exons and the substrate helix. This structural information will be used to explore how metal ions contribute to RNA catalysis and to investigate the chemical transition state of the phosphoryl transfer reactions promoted by this ribozyme. Ribozymes, such as this intron, are the molecules most likely to be the progenitors of modern biological catalysts. Understanding how they promote their reactions will provide valuable insight into enzymological function. The research will provide opportunities for training at the interface of nucleic acid chemistry and structural biology.