RNA-catalyzed thioester synthesis
A series of efficient ribozymes with thioester synthetase activities have been isolated from CoA-linked RNA libraries containing four different lengths (30N, 60N, 100N, and 140N) of random nucleotide regions. Competitive evolution of these size-heterogeneous CoA-RNA libraries resulted in an RNA size population in the order of 30N > 60N >> 100N > 140N. From isolated clones in the 30N and 60N size groups two predominant RNA sequences, TES1 (30N) and TES33 (60N), have been shown to catalyze the synthesis of different thioesters using various acyl adenylates as the substrates. Together with our previous findings, the current results demonstrate a CoA thioester synthetic pathway catalyzed by individual metabolic ribozymes, and suggest a likely mechanism for thioester synthesis and utilization in an RNA world.