Reconstitution of Ribosomes: Studies of Ribosome Structure, Function and Assembly

Abstract

INTRODUCTION
The in vitro reconstitution of the bacterial 30S ribosomal subunit (Traub and Nomura 1968) followed by that of the 50S subunit (Nomura and Erdmann 1970; Fahnestock, Erdmann and Nomura 1973) has established that the information required for the assembly of this complex organelle is entirely contained in the structures of the RNA and protein components. The mechanism involved in this complex self-assembly process is now being elucidated, especially with respect to 30S ribosome assembly, by a variety of in vitro experiments. The in vitro assembly reaction, while differing in some details from in vivo assembly, very likely reflects the in vivo process in important ways. In addition, reconstitution techniques have facilitated the study of ribosome structure and structure-function relationships.

A detailed review on the in vitro reconstitution of 50S subunits (Fahnestock, Held and Nomura 1972), as well as reviews on ribosome assembly in general (Nomura 1970Nomura 1973) have appeared previously. In this article, we summarize and discuss the work related to ribosome assembly, concentrating mainly on the 30S subunit, including several recent developments in this area.

PARTIAL RECONSTITUTION OF RIBOSOMES
The first step in the analysis of the functional role of ribosomal components was the development of a system for reconstituting ribosomes that had been partially disassembled (Staehelin and Meselson 1966; Hosokawa, Fujimura and Nomura 1966), Selective removal of a portion of the ribosomal protein (“split proteins”) was accomplished by centrifugation of the ribosomes in 5 M CsCl in the presence of 0.04 M Mg⁺⁺. The functionally inactive nucleoprotein...