Figure 1

A. Types I, II and III hammerhead ribozymes. Peripheral regions shown as dotted lines contain the tertiary stabilizing motifs and can be of arbitrary sizes. Stems 1, 2 and 3 are indicated. B. The type III hammerhead ribozyme from sTRSV, showing tertiary interactions predicted from comparative sequence analysis, mutational data and computational modeling [2] (pairwise interactions depicted according to ref [22]).