EXPANDING THE SCOPE OF RNA CATALYSIS

The basic notions of transition state theory have been exploited in th e past to generate highly selective catalysts from the vast library of antibody molecules in the immune system. These same ideas were used t o isolate an RNA molecule, from a large library of RNAs, that catalyze s the isomerization of a bridged biphenyl. The RNA-catalyzed reaction displays Michaelis-Menten kinetics with a catalytic rate constant (k(c at)) of 2.8 x 10(-5) per minute and a Michaelis constant (K-m) of 542 mu M; the reaction is competitively inhibited by the planar transition state analog with an inhibition constant (K-i) value of similar to 7 mu M. This approach may provide a general strategy for expanding the s cope of RNA catalysis beyond those reactions in which the substrates a re nucleic acids or nucleic acid derivatives.