Reaction conditions and kinetics of self-cleavage of a ribozyme derived from Neurospora VS RNA.

We have investigated the self-cleavage reaction performed by a ribozyme that contains 164 nucleotides of Neurospora VS RNA. Self-cleavage requires a divalent cation, magnesium being more effective than manganese or calcium. Spermidine or monovalent cations stimulate the reaction but cannot replace magnesium. The temperature optimum is rather broad, around 40-50 degrees C. Unlike some other ribozymes, VS self-cleavage is inhibited by even low concentrations of urea or formamide. The rate of cleavage is the same from pH 5.5 to 8.9, suggesting either that hydroxide is not directly involved in the cleavage chemistry or that a step that precedes the actual cleavage event is rate-limiting.