2 The Pathway and Mechanism of Eukaryotic Protein Synthesis

Abstract

Knowledge of the detailed mechanism of protein synthesis is essential for understanding translational controls. We are primarily concerned with how the various macromolecules of the translational apparatus interact to promote the process of protein synthesis in eukaryotic cells. The entire process is divided conveniently into three phases: initiation, elongation, and termination. This chapter focuses on how the soluble factors, namely, initiation factors, elongation factors, and release factors, catalyze the sequential binding and reaction of aminoacyl-tRNAs to ribosomes as dictated by the template messenger RNA. Details of transfer RNA structure and aminoacylation and ribosome structure lie outside the scope of this chapter. For reviews on the formation and functions of aminoacyl-tRNAs, see Carter (1993) and Söll (1993); see also the chapter by Wool (this volume) on ribosomal proteins and a book on ribosome structure/function (Nierhaus et al. 1993).

Insight into the process of protein synthesis emerged primarily from biochemical studies that utilized radioactively labeled amino acids and fractionated lysates derived from either bacterial or mammalian cells. The major macromolecular components were identified by purifying proteins and nucleic acids required to reconstitute translation in the test tube. Surprisingly, bacterial genetic approaches contributed only modestly to the identification of the greater than 200 macromolecular components that comprise the translational apparatus. Because the biochemical approach was so fruitful, subsequent in vitro studies on how these molecules interact proceeded rapidly. It is only recently that genetic studies with the yeast Saccharomyces cerevisiae or experiments using recombinant DNA techniques have enabled researchers to examine the mechanism...