NMR Studies of a Lead Ribozyme and Its Non-Cleavable Analogue

Abstract

Abstract The structure of a lead ribozyme, which consists of two RNA strands, at neutral pH has been studied by NMR. Nearly all resonances of imino protons, base protons (H2, H5, H6 and H8) and sugar protons (H1′ and H2′) were assigned sequentially. Interesting structural features which deviate from the standard structure were found for the residues at an active site which consists of an internal loop. No indication of stable G:A base pairs was found in the loop. The effect of addition of Pb2+ was studied by the use of a non-cleavable analogue in which the cytidine at a cleavage site is replaced by 2′-O-methylcytidine. It was suggested that Pb2+ binds close to the cleavage site and that the structural change induced by Pb2+ is moderate and localized. #This paper is dedicated to Dr. Yoshihisa Mizuno on the occasion of his 75th birthday.