Table 1.

Observed rate constants (k_obs) of newt and the newt-like hammerhead ribozyme variant previously described²³ and the example env1 identified in our search (env1c). All reactions contained 0.08 µM ³²P-labeled RNA and were supplemented with respective unlabeled RNA to achieve final concentrations listed in the center column. Newt-like designates a construct that is identical to the newt-like construct previously investigated.²³ Fig. S2B and C highlight the differences to the natural newt genomic sequence. No observed rate constant was determined for construct env1c at 0.08 µM RNA because of expected extremely slow speed of ribozyme self-cleavage.

HHR construct	RNA conc. [µM]	kobs [min−1]
newt	0.08	0.0018
	0.8	0.015
	8	0.033
newt-like	0.08	0.00006
	0.8	0.0018
	8	0.012
env1c	0.8	0.0012
	8	0.0024