Ribozyme structures and mechanisms

The past few years have seen exciting advances in understanding the structu re and function of catalytic RNA. Crystal structures of several ribozymes h ave provided detailed insight into the folds of RNA molecules. Models of ot her biologically important RNAs have been constructed based on structural, phylogenetic, and biochemical data. However, many questions regarding the c atalytic mechanisms of ribozymes remain. This review compares the structure s and possible catalytic mechanisms of four small self-cleaving RNAs: the h ammerhead, hairpin, hepatitis delta virus, and in vitro-selected lead-depen dent ribozymes. The organization of these small catalysts is contrasted to that of larger ribozymes, such as the group I intron.