» Articles » PMID: 779767

Turnover As a Control of Ribonucleic Acid Accumulation in Bacteria Undergoing Stepdown

Overview
Journal Biochem J
Specialty Biochemistry
Date 1976 Feb 15
PMID 779767
Citations 1
Authors
Affiliations
Soon will be listed here.
Abstract

The synthesis of ribosomes was compared in rel+ and rel- strains of Escherichia coli undergoing "stepdown" in growth from glucose medium to one with lactate as principal carbon source. Two strains (CP78 and CP79), isogenic except for rel, showed similar behaviour with respect to (1) the kinetics of labelling total RNA and ribosomes with exogenous uracil, (2) the proportion of newly formed protein that could be bound with nascent rRNA in mature ribosomes, and (3) the rate of induction of enzymically active beta-galactosidase (relative to the rate of ribosome synthesis). It was concluded that, as there was no net accumulation of RNA during stepdown in either strain, rRNA turnover must be occurring at a high rate. The general features of ribosome maturation in rel+ and rel- cells were almost identical with those found in auxotrophic rel+ organisms starved of required amino acids. In both cases, there was a considerable delay in the maturation of new ribosomal particles, owing to a relative shortfall in the rate of synthesis of ribosome-associated proteins. Only about 4-5% of the total protein labelled during stepdown was capable of binding with newly formed rRNA. This compared with 3.5% for rel+ and 0.5% for rel- auxotrophs during amino acid starvation. The turnover rate for newly formed mRNA and rRNA was virtually the same in "stepped-down" rel+ and rel- strains and was similar to that of the same fraction in amino acid-starved rel+ cells. The functional lifetime of mRNA was also identical. It seems that in the rel- strain many of the characteristics typical of the isogenic rel+ strain are displayed under these conditions, at least as regards the speed of ribosome maturation and the induction of beta-galactosidase. Studies on the thermolability of the latter enzyme induced during stepdown indicate that inaccurate translation, which occurs in rel- strains starved for only a few amino acids, is less evident in this situation than in straightforward amino acid deprivation.

Citing Articles

Control of protein synthesis in Escherichia coli: analysis of an energy source shift-down.

Johnsen K, Molin S, Karlstrom O, MAALOE O J Bacteriol. 1977; 131(1):18-29.

PMID: 326760 PMC: 235385. DOI: 10.1128/jb.131.1.18-29.1977.

References
1.
Murooka Y, Lazzarini R . In vitro synthesis of ribosomal ribonucleic acid by a deoxyribonucleic acid-protein complex isolated from Escherichia coli. J Biol Chem. 1973; 248(17):6248-50. View

2.
Travers A . Control of ribosomal RNA synthesis in vitro. Nature. 1973; 244(5410):15-8. DOI: 10.1038/244015a0. View

3.
Simon E, Garwes D, Rand J . Reversible inhibition of RNA phage replication and macromolecular synthesis by levorphanol. Biochem Biophys Res Commun. 1970; 40(5):1134-41. DOI: 10.1016/0006-291x(70)90912-5. View

4.
TURNOCK G, Wild D . THE SYNTHESIS OF RIBOSOMES BY A MUTANT OF ESCHERICHIA COLI. Biochem J. 1965; 95:597-607. PMC: 1206783. DOI: 10.1042/bj0950597. View

5.
McCarthy B, Britten R, Roberts R . The Synthesis of Ribosomes in E. coli: III. Synthesis of Ribosomal RNA. Biophys J. 2009; 2(1):57-82. PMC: 1366389. DOI: 10.1016/s0006-3495(62)86841-6. View