ORDER, DYNAMICS AND METAL-BINDING IN THE LEAD-DEPENDENT RIBOZYME

The in vitro selected lead-dependent ribozyme is among the smallest an d simplest of the known catalytic RNA motifs and has a unique metal io n specificity for divalent lead. The conformation and dynamics of this ribozyme are analyzed here by NMR and chemical probing experiments. C omplete assignments of the H-1, C-13 and N-15 resonances have been mad e, and the NMR chemical shift changes in the presence of Pb2+, Mg2+ or high concentrations of Na+ show that there is no significant structur al change upon addition of either activating (Pb2+) or inhibitory (Mg2 +) divalent ions. The C-13 NMR relaxation data indicate substantial dy namic fluctuations on various time-scales for active-site residues in this ribozyme. The combination of chemical probing and NMR experiments reveals a picture of the active site for the lead-dependent ribozyme that has both ordered and dynamic features. (C) 1998 Academic Press.