Figure 6. Interactions between E. coli RPR and the ptRNA cleavage site. Highlighted regions in the secondary structure of E. coli RPR (gray lines within the oval in panel a) interact with the ptRNA specifically at the nucleotide immediately 5′ to the cleavage site and the ACCA sequence at the 3′ terminus (panel b). Dashed lines indicate interactions between the RNA catalyst and the substrate. (Modified, with permission, from Zahler et al. 2005 [©Elsevier].)