The Structure of Eukaryotic Ribosomes

Abstract

I begin with a litany of the gospel. The grand design in research on eukaryotic ribosomes is to know the structure and the function of the organelle: to be able to specify the coordinates, and to define the activity, of each of the molecules in the particle, A subsidiary aim is to compare the structure of eukaryotic and prokaryotic ribosomes. There are significant differences between the two classes of particles. Those differences are the basis of what has been called the “central dilemma”. Eukaryotic ribosomes are appreciably larger: they contain a greater number of proteins, seventy-eighty rather than fiftytwo, and they have an extra molecule of RNA as well. Moreover, the proteins and nucleic acids are, on the average, larger. The difference in size is a paradox since eukaryotic ribosomes perform the same general function, namely to catalyze the synthesis of protein; more to the point, they appear to employ appreciably the same partial reactions, although there may be real differences in the means by which the initiation of peptide synthesis is accomplished. One would like to know the nature of the evolutionary pressure for the accretion of the extra proteins in eukaryotic ribosomes- whether there are functions of the particle still be to uncovered. It has not escaped attention that knowledge of the conserved features may be of help in understanding the function of both eukaryotic and prokaryotic ribosomes.