Figure 5.

Mg²⁺ and spermidine reduce pentamidine inhibition of Ca.LSU catalysis. Equal amounts of radiolabeled Ca.LSU precursor were either assayed for ribozyme activity without preincubation in the presence of varying levels of pentamidine or preincubated before ribozyme assays in buffer alone or in the presence of 1.25 mM MgCl₂, 10 µM GTP or 0.4 mM spermidine. All assays with and without preincubation were performed under standard splicing conditions. Lane P is a sample preincubated in buffer alone without adding splicing components (magnesium, spermidine, GTP).