CRYSTALLOGRAPHIC STRUCTURES OF THE HAMMERHEAD RIBOZYME - RELATIONSHIPTO RIBOZYME FOLDING AND CATALYSIS

The hammerhead ribozyme is a small catalytic RNA that cleaves a target phosphodiester bond in a reaction dependent on divalent metal ions. C rystal structures of the hammerhead reveal the tertiary fold of an enz ymatic ''ground state'' of the molecule; however, they do not clarify the catalytic mechanism of the ribozyme, presumably because a signific ant conformational rearrangement is required to reach an enzymatic tra nsition state. The structural domains seen in the hammerhead can be re lated to sequence or structural mot!fs in transfer and ribosomal RNAs, suggesting that they represent tertiary building blocks that will be found in large, complex RNAs.