RIBOSOME STRUCTURE AND FUNCTIONAL SITES

Abstract

This chapter elaborates the ribosome structure and functional sites. The structure of the large and small subunits is described. The small subunit is divided into two unequal parts by an indentation, and a region of accumulated negative stain. The parts are referred to as the upper one-third and the lower two-thirds. A region of the subunit, called the platform, extends from the lower two-thirds of the small subunit, and forms a cleft between it, and the upper one third. This cleft is an important functional region of the small subunit, and has been proposed as the site of the codonanticodon interaction, and as a part of the binding site of initiation factors IF1, IF2, and IF3. It is found that since protein locations determined by immunoelectron microscopy critically depend upon the model used to map them, protein locations differ markedly from those of the Berlin group for both small and large subunits, and the functional implications are completely different). The large subunit, like the small subunit, is asymmetric. It consists of a central protuberance and projections inclined at approximately 50° from the central protuberance.