Figure 4.

Crowding increases ribozyme activity. Formation of the native state (N) was measured in single-turnover activity assays (Supplementary Figure S4). The fraction of substrate cleaved versus [Mg²⁺] in three or more trials were fit to a two-state function. See Supplementary Figure S6 for further data on other mutants. (a) The product formed in 25 s indicates the fraction of native ribozyme at each [Mg²⁺]. The mutants and WT fold similarly in 18% PEG, but the mutants have lower maximum activity. (b) Product formed in 3 min indicates the total population competent to react. PEG only partially compensates for destabilizing mutations in this assay, indicating a greater fraction of misfolded RNAs.