A decade of progress in understanding the structural basis of protein synthesis

The key reaction of protein synthesis, peptidyl transfer, is catalysed in a ll living organisms by the ribosome - an advanced and highly efficient mole cular machine. During the last decade extensive X-ray crystallographic and NMR studies of the three-dimensional structure of ribosomal proteins, ribos omal RNA components and their complexes with ribosomal proteins, and of sev eral translation factors in different functional states have taken us to a new level of understanding of the mechanism of function of the protein synt hesis machinery. Among the new remarkable features revealed by structural s tudies, is the mimicry of the tRNA molecule by elongation factor G, ribosom al recycling factor and the eukaryotic release factor 1. Several other tran slation factors, for which three-dimensional structures are not yet known, are also expected to show some form of tRNA mimicry. The efforts of several crystallographic and biochemical groups have resulted in the determination by X-ray crystallography of the structures of the 30S and 50S subunits at moderate resolution, and of the structure of the 70S subunit both by X-ray crystallography and cryo-electron microscopy (EM). In addition, low resolut ion cryo-EM models of the ribosome with different translation factors and t RNA have been obtained. The new ribosomal models allowed for the first time a clear identification of the functional centres of the ribosome and of th e binding sites for tRNA and ribosomal proteins with known three-dimensiona l structure. The new structural data have opened a way for the design of ne w experiments aimed at deeper understanding at an atomic level of the dynam ics of the system. (C) 2000 Elsevier Science Ltd. All rights reserved.