Correct folding of a ribozyme induced by nonspecific macromolecules

The 50‐nucleotide hammerhead ribozyme HH‐S was tested for self‐cleavage. The self‐cleavage was very inefficient, and only 13% of HH‐S was transformed to its cleavage products. Surprisingly, the percentage of cleavage of HH‐S was increased to 30% when 1 µg of tRNA was added to the reaction mixture (6 µL). Other macromolecules such as DNAs and proteins were examined to see if they also augmented cleavage of HH‐S , and it was found that most of the macromolecules tested, except nucleotide monomers, did indeed enhance HH‐S cleavage. The self‐cleaving reaction was almost saturated in 30 min, and only 13% of HH‐S was cleaved at 37 °C for a 70‐min reaction, indicating that 87% of HH‐S was in kinetically trapped inactive conformations. Time courses for the reaction of the HH‐S self‐cleavage were also measured in the presence of tRNA, an oligodeoxyribonucleotide, or BSA. Cleavage of HH‐S, which had already reached a plateau of 13% cleaved, increased gradually after the addition of the effector molecules. The first‐order rate constant for the self‐cleavage reaction in the absence of an effector was comparable to that in the presence of BSA, indicating that the effector molecules do not affec