Dynamics of a Gronp I Ribozyme Detected by Spectroscopic Methods

Little is known about RNA dynamics, even though it is likely that dynamics are important for both folding Olnd function, The ribozyme, L·2l Seal, derived from the group I intean of Tetrahymena thermophila (Zaug et at 1988; Kay and Inoue 1987) provides an excellent system for studying dynamics, since ilS secondary structure is known (Michel and Dujon 1983: Burke et al. 1987; Cech et al. 19(4) nnd a good model is available for its three-dimensional structure (Michel and Westhof 19(0). Moreover, spectroscopic probes have been developed that arc sensitive to binding of substrate by this rihozyme (Sugimoto et 111.198%; Bevilacqua et aI.1992; Kierzek el al. 1993). This permits detection uf intermediates and measurement of rate constants for various interconversions. The effects of substitutions and of solution condilions on these ratc constants give insights into relationships between structure. and dynamics and function. The RNA mution most intensively studied thus far in this system is docking: of substrate into the catalytic core of the rihozyme (Bevilacqua et aJ. 1992, 1993. ] 994; Li ct al. .995; Li, Profcnno and Turner. unpub!' results). This chapter reviews the methods and results of these studies, and discusses some futliTe perspectives.