Ribosome Formation in Escherichia coli

Abstract

INTRODUCTION
During the formation of an organelle that involves more than 70 interacting elements, some steps might be expected to occur indifferently with respect to others, while others are rate-limiting. In theory, any step can become rate-limiting if a component is in short supply, or if a jam-up of a series of complex steps occurs. The purpose of this chapter is to try to analyze which steps are rate-limiting for ribosome formation during exponential growth and how various other events are timed in relation to the rate-limiting ones.

In an attempt to order the facts, opinions and preferences are stated below. However, they are clearly labeled and segregated in order to make it easier to ignore or spurn them as further evidence accumulates. Also, there are only oblique references to comparisons of E. coli and eukaryotic paradigms. The attentive reader may notice the appearance in the discussion of E. coli of a large RNA that contains both 16S- and 23S-specific sequences. In further analogy to eukaryotic cells, the large RNA precursor can be split in absence of protein synthesis, and final maturation steps in the formation of 30S ribosomes may occur “out in the cytoplasm,” etc. Nevertheless, the eukaryotic rRNAs are still of different size, have different methylation patterns, and cannot substitute for bacterial rRNA in reconstitution reactions: oversimplifiers, beware!

Much of the material and preliminary discussion is covered in recent review articles by Pace (1973) and Nomura (1970 and Nomura (1973). The nomenclatures current there for precursors of rRNA species or...