A Functional Model for the Ribosome

The “ice” structure for theE. coliribosome clearly illustrates how the ribosome could work and it is used as the basis of a detailed account of ribosome function. There have been objections to this structure as it does not fit with current beliefs about the position of the T-site, for the arriving tRNA, or the Exit-site: these beliefs are wrong. The elongation factor EF-Tu is required at both the T-site and the E-site, and these two attachment areas were combined into the false site. The E-site has been placed as the L1-ridge because deacylated tRNAs attach to protein L1, but none of these experiments used a cognate codon to get a positive identification of this as the E-site. The reason L1 attaches to deacylated tRNAs is that it is at the E-site in polysomes, which contain closely stacked, or overlapping, ribosomes with the L1-ridge at the interface between ribosomes. The revised data allows the 1989 ribosome model to be reconciled with the most contradictory results and it is then used to develop a more detailed picture of the ribosome.