Structure of the catalytic core of the Tetrahymena ribozyme as indicated by reactive abbreviated forms of the molecule.

The precursor rRNA of Tetrahymena thermophila contains a group I intervening sequence (IVS) that catalyzes its own excision to yield mature rRNA. The excised IVS catalyzes a number of cleavage/ligation reactions that are analogous to the transesterification reactions of splicing. We examined the behavior of a variety of 3'-truncated forms of the IVS and found several abbreviated molecules that retained catalytic activity. The reactivity of these molecules indicates that the site at which cleavage/ligation occurs lies in close proximity to all of the conserved sequence elements within the catalytic core of the IVS.