When the circular form of the self-splicing intervening sequence of Tetrahymena thermophila was purified by denaturing polyacrylamide gel electrophoresis by standard methods, the rate of its reaction with tetrauridylate decreased 150-fold at 30 °C and at least 1000-fold at 0 °C. The activity of the self-splicing RNA was restored by heating it to high temperature and letting it renature in the presence of Mg2+. The rate of reaction of tetrauridylate with the self-splicing RNA flanked by exons was also greatly decreased by gel purification. the difference in activation energies for the reaction of native and denatured intervening sequences suggests that a substantial conformational rearrangement of the gel-purified RNA occurs prior to reaction.
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