Efficient 50S ribosome-catalyzed peptide bond synthesis with an aminoacyl minihelix

RNA minihelices that recreate the amino acid acceptor domain of the two-dom ain L-shaped tRNA molecule are substrates for specific aminoacylation by tR NA synthetases. Some lines of evidence suggest that this domain arose indep endently of and predated the second, anticodon-containing domain. With puro mycin and a minihelix charged with alanine, we show here efficient 50S ribo some catalyzed peptide synthesis. The aminoacyl minihelix is as active as a minoacyl tRNA in the synthetic reaction. The high efficiency of the charged minihelix is due to a relatively strong interaction with the 50S particle. In contrast, an aminoacyl RNA fragment that recreates the 3-side of the tR NA acceptor stem has a muchweaker interaction with the 50S particle. These results are consistent with the minihelix domain being the major loci for t RNA interactions with the 50S ribosome. They may also have implications for the historical development of RNA-based systems of peptide synthesis.