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Ribozymes, the first 20 years.

In 1982 we reported the first catalytic RNA or ribozyme: the self-splicing intron of the Tetrahymena pre-rRNA. Additional examples of natural ribozymes were soon found, and research in the field focused on their enzymic mechanism and secondary and tertiary structure. Ribozymes identified through in vitro selection extended the repertoire of RNA catalysis. Two directions of current and future interest are the determination of atomic-resolution structures of large ribozymes by X-ray crystallography and the structural and mechanistic analysis of complexes of ribozymes with protein facilitators of their activity.