Mg2+-dependency of the Helical Conformation of the P1 Duplex of the Tetrahymena Group I Ribozyme

Abstract

The P1 duplex of Tetrahymena group I ribozyme is the important system for studying the conformational changes in folding of ribozyme. The formation of the P1 duplex between IGS and substrate RNA and the catalytic activity of ribozyme require a variety of metal ions such as Mg2+ and Mn2+. In order to investigate the effect of the Mg2+ concentration on the conformation of the P1 duplex, the NMR study was performed as a function of Mg2+ concentration. This study revealed that the less stable AU-rich region formed duplex at 50 degrees C under high Mg2+ concentration condition but melts out under low Mg2+ concentration condition. It was also found that in the active conformation under 10 mM MgCl2 condition, the unstable central G-U wobble pair maintains the significant base pairing up to 50 degrees C. This study provides the information of the unique feature of the P1 duplex structure and the roll of Mg2+ ion on the formation of the active conformation.