The Pools of Ribosomal Proteins and Ribosomal Ribonucleic Acids During Relaxed Control of Escherichia coli A19 (Hfr, rel met rns)

Abstract

149 ~~ ~~ ~The soluble fraction extracted from Escherichia coli A19 (Hfr, rel met rns) during early and late times of phenotypic and genotypic induced relaxed control have been examined for the possible accumulation of ribosomal proteins (r-proteins) and rRNA species during this time of unbalanced macromolecular synthesis. Ribosomal proteins and rRNA species were not found to accumulate within the soluble fraction at any time during this period of relaxed control; even after the typical rRNA accumulation had ceased, r-proteins did not accumulate. It is concluded, from these and related observations, that the r-proteins and rRNA species known to be produced during relaxation must immediately associate to form the unusual ribonucleoprotein particles (e.g. ' relaxed particles' and ' chloramphenicol particles') characteristic of periods of relaxed control. Since r-proteins do not accumulate even when net RNA accumulation halts, it appears that some elements of the normal, basic co-ordination between rRNA and r-protein synthesis/stability persist even during relaxed control.

Authentic precursors to ribosomal subunits accumulate in Escherichia coli in the absence of functional DnaK chaperone

“…Late ribosomal proteins must therefore come from a pre‐existing pool, in which they are either free or present in a structure such as an rrn transcription antitermination complex (Torres et al ., 2001), the ClpXP protease (see Table 1 in Flynn et al ., 2003) or the polyphosphate–protease Lon complex (Kuroda et al ., 2001) or from the instantaneous recycling of proteins released by the turnover of pre‐existing ribosomes (Cheng and Deutscher, 2003). It is generally agreed that there is no significant pool of free ribosomal proteins in growing E. coli cells (Gupta and Singh, 1972; Gausing, 1974; Marvaldi et al ., 1974; Ulbrich and Nierhaus, 1975; Sykes and Metcalf, 1979), and the exchange of some ribosomal proteins between ribosomes has been described in only a very few cases (Ulbrich and Nierhaus, 1975; Robertson et al ., 1977; Subramanian and van Duin, 1977). Other situations in which the recycling of ribosomal proteins has been demonstrated (Nakada and Marquisee, 1965; Lefkovits and Di Girolamo, 1969; Tal et al ., 1977) or deemed doubtful (Adachi and Sells, 1979) have been described.…”