An alternative model for the elongation cycle of protein biosynthesis

Abstract

For the last twenty years ribosomal functions have been discussed in the framework of a ribosome model comprising two tRNA binding sites, an A site for aminoacyl-tRNA and a P site for peptidyl-tRNA. The recent discovery of a third binding site, the E site, specific for deacylated tRNA, has led to a three-site model for the elongation cycle. The essential feature of this model is the presence of two tRNAs on the ribosome before and after translocation. The model has important implications for tRNA release and the translocation reaction.