Ribozyme-catalysed amino-acid transfer reactions

THE 'RNA world' hypothesis proposes an early stage in the evolution of life in which both genomic and catalytic functions were fulfilled by RNA(1). The evolution of RNA-catalysed protein synthesis would have been a necessary step in the transition from such an RNA world to modern protein-dominated biology, For this to have been possible, RNA must be capable of catalysing amide-bond formation using acylated carrier RNA substrates as amino-acid donors. We have used in vitro selection and evolution to isolate ribozymes with acyl transferase activity from a pool of random RNA sequences. One of these acyl transferases with a 5'-amino group transfers an amino acid to itself in a reaction that we propose to be analogous to peptidyl transfer on the ribosome.