Diverse RNA substrates for aminoacylation: clues to origins?

Abstract

The aminoacylation of RNA structures generally is considered the starting point for the emergence of the theater of proteins from the RNA world. Once an aminoacyl ester linkage is established with an RNA acceptor, peptide bond formation is thermodynamically favored. In contemporary protein biosynthesis, aminoacylation is directed to the 3′-end of the tRNA structure, which, in turn, brings the activated amino acid to the ribosomes for addition to the growing polypeptide chain. But during the last 9 years a variety of artificial RNA substrates for aminoacylation has been reported (1–8). And in this issue of the Proceedings, the list of examples is expanded in a significant way. Felden and Giege (9) describe for the first time an aminoacylation system based on a circular RNA substrate. The results obtained with this novel substrate add further support to the idea that the contemporary system of tRNA aminoacylation could have grown out of early aminoacylation systems that used diverse RNA oligonucleotide substrates. Interactions between some of these aminoacylated substrates could have led to a primitive system of peptide synthesis.